# Retell AI

> Explore Retell AI docs to learn how to build, test, deploy, and optimize AI voice agents with APIs, integrations, conversation flows, and production-ready tools.

- [Introduction to Retell](https://docs.retellai.com/general/introduction.md): Retell is a platform to build, test, deploy, and monitor AI voice and chat agents with telephony, prompts, tools, and analytics built in.
- [Build your first phone agent in 15 minutes](https://docs.retellai.com/get-started/quick-start.md): Build your first Retell AI phone agent in 15 minutes: create an account, pick a template, test in the dashboard, deploy to a phone number, and make a call.
- [Retell AI Conductor overview](https://docs.retellai.com/conductor/overview.md): Use Retell AI Conductor to build agents, improve analytics dashboards, investigate conversations, and open resources while keeping your work in context.
- [Build and refine agents](https://docs.retellai.com/conductor/build-and-refine.md): Build and refine agents with Retell AI Conductor. Describe an edit, compare the current and proposed settings, and accept changes before testing your agent.
- [Test and improve agents](https://docs.retellai.com/conductor/test-and-improve.md): Use Retell AI Conductor to investigate calls and chats, run simulation tests, and review results. Find issues and refine agent responses before deployment.
- [Inspect knowledge bases](https://docs.retellai.com/conductor/knowledge-base.md): Inspect knowledge bases with Retell AI Conductor. Find sources, check indexing status and errors, and see which knowledge bases your agents and nodes use.
- [Review calls and chats](https://docs.retellai.com/conductor/call-and-chat-history.md): Investigate calls and chats with Retell AI Conductor. Filter conversations, inspect transcripts and tool calls, and compare failures to find agent improvements.
- [Build analytics dashboards](https://docs.retellai.com/conductor/analytics-dashboards.md): Build analytics dashboards with Retell AI Conductor. Describe the metrics you need, attach charts for context, and review proposed changes before applying them.
- [Review QA results](https://docs.retellai.com/conductor/ai-qa.md): Review AI QA results with Retell AI Conductor. Inspect cohort trends and individual evaluations, compare findings with call transcripts, and identify fixes.
- [Review contacts](https://docs.retellai.com/conductor/contacts.md): Inspect contacts with Retell AI Conductor. Find records, review contact fields, and follow associated phone calls and SMS chats across agents in your workspace.
- [Pricing](https://docs.retellai.com/conductor/usage-and-billing.md): Understand Retell AI Conductor’s daily free messages, enable pay-as-you-go after they run out, and set a monthly spending limit for your workspace.
- [Build a Retell agent: configuration overview](https://docs.retellai.com/build/overview.md): Start building a Retell agent: pick an agent type, then configure the rest, including speech recognition, LLM responses, voice, and telephony behavior.
- [Single/Multi Prompt Agent Overview](https://docs.retellai.com/build/single-multi-prompt/prompt-overview.md): Choose between Retell single-prompt and multi-prompt agents based on call complexity — simple single prompt or staged prompts for state-driven conversations.
- [Write a single prompt](https://docs.retellai.com/build/single-multi-prompt/write-single-prompt.md): Write a Retell single prompt agent using sectional prompts and clear instructions so the agent reliably follows your script across the full phone conversation.
- [Build a multi-prompt agent](https://docs.retellai.com/build/single-multi-prompt/write-multi-prompt.md): Build a Retell multi-prompt agent by breaking the conversation into prompted states with explicit transitions between them — like a lead qualification flow.
- [Step 2: Configure basic agent settings](https://docs.retellai.com/build/single-multi-prompt/configure-basic-settings.md): Set up a Retell single or multi-prompt agent: choose the language model, pick a voice and speaking speed, and decide who speaks first on the call.
- [Function calling for single and multi-prompt agents](https://docs.retellai.com/build/single-multi-prompt/function-calling.md): Function calling lets Retell single or multi-prompt agents take real actions — transfer calls, end calls, book appointments, send SMS, and call external APIs.
- [End call](https://docs.retellai.com/build/single-multi-prompt/end-call.md): Configure the End Call tool in Retell AI to hang up when a conversation is complete and send optional custom SIP headers with call outcomes or reference IDs.
- [Transfer call tool (single & multi-prompt agents)](https://docs.retellai.com/build/single-multi-prompt/transfer-call.md): Add the Transfer Call tool to a Retell single or multi-prompt agent to route calls to a human, with cold, warm, and agentic warm transfer modes.
- [Send SMS](https://docs.retellai.com/build/single-multi-prompt/send-sms.md): Use the Send SMS tool so a Retell single or multi-prompt agent can text the caller or another number mid-call from SMS-enabled Retell or imported numbers.
- [Press digit (IVR navigation)](https://docs.retellai.com/build/single-multi-prompt/press-digit.md): Enable Retell single or multi-prompt agents to navigate DTMF-input IVR menus by pressing keypad digits during outbound calls to reach the right department.
- [Integrate any system with custom function](https://docs.retellai.com/build/single-multi-prompt/custom-function.md): Add a custom function to a Retell single- or multi-prompt agent to call your API mid-call. Configure URL, method, headers, parameters, and responses.
- [Integration tools](https://docs.retellai.com/build/single-multi-prompt/integration-tools.md): Add HubSpot, Salesforce, Zendesk, or Cal.com tools to a Retell AI prompt agent: connect once, configure inputs and outputs, and test with live data.
- [Code tool: run JavaScript in a Retell agent](https://docs.retellai.com/build/single-multi-prompt/code-tool.md): Add a Code tool to a single- or multi-prompt Retell agent to run JavaScript, read dynamic variables and metadata, call HTTP APIs, and store results.
- [Extract Dynamic Variables](https://docs.retellai.com/build/single-multi-prompt/extract-dv.md): Add the Extract Dynamic Variable tool to a Retell single- or multi-prompt agent to capture values from a call as typed dynamic variables.
- [Agent Transfer tool: hand a call to another AI agent](https://docs.retellai.com/build/single-multi-prompt/transfer-agent.md): Add the Agent Transfer (agent swap) tool to a Retell single or multi-prompt agent so it can hand the live call to another AI agent mid-conversation.
- [MCP tools for single and multi-prompt agents](https://docs.retellai.com/build/single-multi-prompt/mcp.md): Connect a Retell single- or multi-prompt agent to a remote MCP server so it can call the server's tools during a live voice or chat conversation.
- [Conversation flow agents: structured voice AI call control](https://docs.retellai.com/build/conversation-flow/overview.md): Build structured Retell voice agents with conversation flow — nodes for dialogue, tools, transfers, code, and transitions for precise call control.
- [Configure global settings](https://docs.retellai.com/build/conversation-flow/global-setting.md): Configure global settings for a Retell conversation flow agent — voice, language, LLM, denoising, and other agent-level options on the empty canvas.
- [Nodes and edges](https://docs.retellai.com/build/conversation-flow/node.md): Nodes are the building blocks of Retell conversation flows. Learn every node type, how edges connect them, and how transition conditions advance calls.
- [Conversation node](https://docs.retellai.com/build/conversation-flow/conversation-node.md): Use Retell conversation nodes for multi-turn dialogue without tool calls — the default building block for capturing info and guiding callers through a flow.
- [Subagent node](https://docs.retellai.com/build/conversation-flow/subagent-node.md): Subagent nodes let a Retell conversation flow combine dialogue with on-the-fly tool calls — the LLM decides whether and when to use each attached tool.
- [Call a function from a conversation flow node](https://docs.retellai.com/build/conversation-flow/function-node.md): Run a pre-built function, integration tool, or custom function from a Retell conversation flow function node; it fires on entry and transitions on the result.
- [Custom function in conversation flow](https://docs.retellai.com/build/conversation-flow/custom-function.md): Add a custom function to a Retell conversation flow to call your external API mid-call. Configure method, URL, headers, parameters, and responses.
- [Integration tools in conversation flow](https://docs.retellai.com/build/conversation-flow/integration-tools.md): Call HubSpot, Salesforce, Zendesk, or Cal.com tools from a Retell AI conversation flow function node, and branch transitions on what comes back.
- [Code node: run JavaScript in a conversation flow](https://docs.retellai.com/build/conversation-flow/code-node.md): Add a Code node to a Retell conversation flow to run JavaScript, read dynamic variables and metadata, call HTTP APIs, and store results.
- [Call transfer node in conversation flow](https://docs.retellai.com/build/conversation-flow/call-transfer-node.md): Use a call transfer node to hand a Retell phone call off to a different number. Supports Retell and imported numbers, with optional pre-transfer messages.
- [Press Digit Node](https://docs.retellai.com/build/conversation-flow/press-digit-node.md): Press digit nodes let Retell agents navigate IVR menus by inferring and pressing the correct keypad digit silently during an outbound phone call.
- [End node](https://docs.retellai.com/build/conversation-flow/end-node.md): Use an end node in a Retell conversation flow to terminate the call cleanly, optionally with a closing message generated from a prompt or static text.
- [Logic Split Node](https://docs.retellai.com/build/conversation-flow/logic-split-node.md): Use a logic split node to branch a Retell conversation flow on rules — the agent evaluates conditions on entry and routes silently to the next node.
- [SMS Node](https://docs.retellai.com/build/conversation-flow/sms-node.md): Use an SMS node to have a Retell voice agent send a text mid-call — to the caller or a different number — using an SMS-approved Retell or imported number.
- [Extract Dynamic Variable Node](https://docs.retellai.com/build/conversation-flow/extract-dv-node.md): Add an extract dynamic variable node to a Retell conversation flow to pull values from the dialogue and store them as text, number, boolean, or enum variables.
- [Agent Transfer Node](https://docs.retellai.com/build/conversation-flow/transfer-agent-node.md): Agent transfer nodes (agent swap) hand a Retell call from one AI agent to another, useful for specialized agents, language switches, and modular call flows.
- [MCP node in conversation flow](https://docs.retellai.com/build/conversation-flow/mcp-node.md): Add an MCP node to a Retell conversation flow to call remote MCP server tools during a live call, with custom headers and authentication.
- [Transition conditions](https://docs.retellai.com/build/conversation-flow/transition-condition.md): Control when a Retell conversation flow agent moves between nodes: prompt conditions evaluated by the LLM, deterministic equation conditions, and else edges.
- [Reusable subflows for conversation flow agents](https://docs.retellai.com/build/conversation-flow/components.md): Package parts of a conversation flow into reusable Retell subflows, so you can build complex agents once and share consistent logic across many flows.
- [Flex Mode: dynamic conversation flow execution](https://docs.retellai.com/build/conversation-flow/flex-mode.md): Flex Mode compiles a Retell conversation flow into a single structured prompt at runtime so the agent can handle varied user behavior while keeping flow logic.
- [Global Node](https://docs.retellai.com/build/conversation-flow/global-node.md): Global nodes in a Retell conversation flow can be reached from anywhere in the agent — ideal for handling universal intents like callbacks and human handoff.
- [Finetune Examples](https://docs.retellai.com/build/conversation-flow/finetune-examples.md): Add finetune examples to Retell conversation, subagent, and function nodes to correct unexpected responses or transitions with concrete transcript snippets.
- [Debug guide](https://docs.retellai.com/build/conversation-flow/debug-guide.md): Diagnose and fix Retell conversation flow agent issues — wrong responses, missed transitions, and prompt problems — with a step-by-step guide.
- [Create chat agent](https://docs.retellai.com/build/create-chat-agent.md): Build a Retell chat agent in the dashboard or API for text conversations, convert a voice agent to chat, and deploy via web widget, SMS, or API.
- [Agent workflow](https://docs.retellai.com/agent/agent-workflow.md): Run pre-call and post-call functions on a Retell AI agent: look up the caller before the agent speaks, then log the outcome and create follow-ups.
- [Set language for your agent](https://docs.retellai.com/agent/language.md): Set a single language for a Retell agent to control speech recognition, voice pronunciation, and the language the agent uses to respond during calls.
- [Configure a multilingual agent](https://docs.retellai.com/agent/multilingual.md): Configure a Retell multilingual agent: pick which languages it supports, understand ASR and TTS accuracy trade-offs, and when single-language is a better fit.
- [Supported languages by provider](https://docs.retellai.com/build/language-support.md): Which Retell text-to-speech and speech recognition providers support each language, with the codes accepted by the API and model-level restrictions.
- [Speech recognition providers](https://docs.retellai.com/build/asr-providers.md): An overview of Retell's speech recognition providers — Azure, Deepgram, and Soniox — and how Retell auto-routes based on your agent's configured languages.
- [Balance between transcription accuracy and latency](https://docs.retellai.com/build/transcription-mode.md): Pick the right Retell transcription mode to balance accuracy against latency — interim results for speed or context-aware results for higher accuracy.
- [Handle background speech & noise](https://docs.retellai.com/build/handle-background-noise.md): Tune Retell denoising modes, interruption sensitivity, and background noise handling so your voice agent stays accurate in loud or noisy environments.
- [Agent Handbook](https://docs.retellai.com/build/agent-handbook.md): Turn on Retell Agent Handbook presets to add best-practice prompts for personality, accuracy, and safety with one toggle — no manual prompt writing required.
- [Conversational Mode](https://docs.retellai.com/build/conversational-mode.md): See how Conversational Mode rephrases your voice agent's replies — shorter, more natural, and more human than a typical assistant.
- [Prompt Engineering Guide](https://docs.retellai.com/build/prompt-engineering-guide.md): Best practices for writing Retell agent prompts that produce reliable, natural-sounding phone conversations — structure, examples, edge cases, and pitfalls.
- [Prompt guide & examples for specific situations](https://docs.retellai.com/build/prompt-situation-guide.md): Prompt examples for common voice agent situations — phone numbers, emails, dates, spellings, confirmations — many also available as Agent Handbook presets.
- [Configure LLM Options](https://docs.retellai.com/build/llm-options.md): Tune Retell LLM settings — temperature, fast tier, structured output, retries, timeouts — to balance reliability, latency, and cost for your voice agent.
- [Choose a custom voice](https://docs.retellai.com/build/voice.md): Add custom voices to your Retell agent — search ElevenLabs community voices, import a voice clone, or train a clone for a unique brand-specific sound.
- [Platform voices](https://docs.retellai.com/build/platform-voices.md): Retell platform voices are a curated library tuned for phone conversations — clear at telecom bitrates, with automatic TTS fallback and no extra setup.
- [Expressive Mode: add emotion and emphasis to agent speech](https://docs.retellai.com/build/expressive-mode.md): Turn on Expressive Mode so Retell voice agents add emotion tags, sighs, pauses, and stressed words automatically or with manual overrides in your prompt.
- [TTS provider comparison](https://docs.retellai.com/build/tts-provider-comparison.md): Compare Retell's TTS voice providers, including platform voices, MiniMax, Cartesia, Inworld, ElevenLabs, and OpenAI, on models, features, and languages.
- [Add custom pronunciation](https://docs.retellai.com/build/add-pronunciation.md): Control how Retell AI agents pronounce words with IPA, CMU, Mandarin Pinyin, or Cantonese Jyutping based on the selected voice provider and model.
- [Make agent pause and respond with nothing](https://docs.retellai.com/build/no-response.md): Keep a Retell agent silent on demand with the NO_RESPONSE_NEEDED stop sequence, so it pauses for the caller without speaking or interrupting.
- [Add pause or read slowly](https://docs.retellai.com/build/add-pause.md): Control speech pacing in Retell agents by adding spaced dashes for short pauses and longer Read Slowly markup for phone numbers, addresses, and confirmations.
- [Setup TTS fallback](https://docs.retellai.com/build/tts-fallback.md): Configure TTS fallback voices so Retell agents keep speaking during a TTS provider outage — required when using custom or third-party provider voices.
- [Handle voicemail and IVR](https://docs.retellai.com/build/handle-voicemail.md): Configure Retell agents to detect voicemails and IVR systems on outbound calls and choose what to do next — hang up, leave a message, or navigate the menu.
- [Capture DTMF input from user](https://docs.retellai.com/build/user-dtmf.md): Capture DTMF keypad input from callers in Retell agents — accept PINs, menu choices, and numeric entries, and configure completion timing and digit counts.
- [Set & parse custom SIP headers](https://docs.retellai.com/build/telephony/sip-headers.md): Use custom SIP headers in Retell AI to pass metadata on inbound calls, outbound calls, transfers, and agent hangups, with dynamic values from the conversation.
- [Knowledge base setup and retrieval tuning](https://docs.retellai.com/build/knowledge-base.md): Attach URLs, documents, and custom text to a Retell agent, then tune retrieval with query-rewrite instructions so it answers calls with accurate context.
- [Dynamic variables: personalize Retell agent calls](https://docs.retellai.com/build/dynamic-variables.md): Inject per-call data into Retell agents using `{{variable_name}}` syntax for personalized greetings, context-aware responses, and dynamic call routing.
- [Guardrails](https://docs.retellai.com/build/guardrails.md): Use Retell guardrails to detect prohibited topics in agent responses and user input, replacing flagged content with a safe placeholder so calls continue.
- [Testing overview](https://docs.retellai.com/test/test-overview.md): Compare Retell's agent testing methods — LLM Playground, simulation, batch, web call, and phone call testing — and pick the right one for each stage.
- [Manually test your agent](https://docs.retellai.com/test/llm-playground.md): Test a Retell agent in the LLM Playground: chat manually or with an AI-simulated user, inspect tool calls and transitions, and replay any turn.
- [Debug your agent response](https://docs.retellai.com/test/llm-playground-debug.md): Debug a Retell agent in the LLM Playground: open Debug on any response or transition, apply suggested fixes, and regenerate the turn to verify.
- [Automatically test your agent](https://docs.retellai.com/test/llm-simulation-testing.md): Test a Retell agent with LLM simulation: an AI-simulated user runs your scenario in a text conversation, and success criteria grade each run.
- [Batch test your agent](https://docs.retellai.com/test/batch-test-simulation.md): Run Retell batch tests on many simulation cases at once, then review pass rate and per-case results in Batch Testing History to catch regressions.
- [Web call testing](https://docs.retellai.com/test/test-web.md): Test a Retell voice agent with a browser web call from the dashboard: use the Test Audio panel to hear real audio, latency, and interruptions.
- [Phone call testing](https://docs.retellai.com/test/test-phone.md): Test a Retell voice agent on a real phone call: attach a number, place an outbound test call or dial in, and validate audio, latency, DTMF, and transfers.
- [Testing with Conductor](https://docs.retellai.com/test/testing-with-conductor.md): Use Conductor, Retell's AI copilot, to generate simulation test cases from real calls, cold-start suites for new agents, and target tool calls.
- [Testing pricing](https://docs.retellai.com/test/testing-pricing.md): How Retell bills agent testing: text tests (Playground, simulation, batch) cost per message and voice tests (web, phone) cost per minute at production rates.
- [Purchase phone number](https://docs.retellai.com/deploy/purchase-number.md): Purchase Retell-managed US or Canada phone numbers directly in the dashboard — no telephony provider account required, ready for inbound and outbound calling.
- [A/B Testing](https://docs.retellai.com/deploy/ab-testing.md): Run Retell A/B tests by splitting inbound and outbound voice and chat traffic between agents to compare prompts, voices, and flows in production.
- [Connect Retell voice agents to custom telephony](https://docs.retellai.com/deploy/custom-telephony.md): Integrate Retell voice agents with your own telephony provider using elastic SIP trunking or imported numbers from Twilio, Telnyx, and Vonage.
- [Connect a Twilio number to Retell with elastic SIP trunking](https://docs.retellai.com/deploy/twilio.md): Connect Retell to your Twilio account using elastic SIP trunking. Set up termination, origination, credentials, and import Twilio numbers into Retell.
- [Telnyx](https://docs.retellai.com/deploy/telnyx.md): Connect Retell to a Telnyx account with elastic SIP trunking — create the trunk, configure FQDN routing, set up outbound auth, and import Telnyx numbers.
- [Vonage](https://docs.retellai.com/deploy/vonage.md): Connect Retell to a Vonage account using SIP trunking — configure termination and origination, set up credentials, and import Vonage numbers for calling.
- [Avaya](https://docs.retellai.com/deploy/avaya.md): A step-by-step guide to integrate Avaya Aura with Retell's SIP endpoints using Avaya SBCE as the border element to send and receive phone calls.
- [Connect Genesys Cloud to Retell](https://docs.retellai.com/deploy/genesys.md): Set up a Genesys Cloud SIP phone trunk, number plans, and outbound routes to send inbound and outbound calls between Genesys and Retell agents.
- [Connect Five9 to Retell](https://docs.retellai.com/deploy/five9.md): Connect Five9 to Retell AI over the pre-built SIP trunk: import your Five9 number, add a ThirdPartyTransfer node, and route IVR calls to a voice agent.
- [Amazon Connect](https://docs.retellai.com/deploy/amazon-connect.md): Amazon Connect is a cloud-based contact center service from AWS that lets you set up and manage customer support call centers quickly.
- [Make outbound calls](https://docs.retellai.com/deploy/outbound-call.md): Make outbound phone calls with Retell agents — bind agents to your numbers, prepare API credentials, and trigger calls programmatically or from the dashboard.
- [Receive calls](https://docs.retellai.com/deploy/inbound-call.md): Bind voice agents to Retell or imported numbers to answer inbound calls, route SIP traffic, handle overflow, and pass per-call context.
- [Inbound call & SMS webhook](https://docs.retellai.com/features/inbound-call-webhook.md): Use the Retell inbound webhook to dynamically pick the agent, set dynamic variables, reject calls, and pass per-call context for inbound phone and SMS.
- [International calling](https://docs.retellai.com/deploy/international-call.md): International calling rates and supported countries for Retell-managed numbers, plus how to enable outbound calls to global destinations from your workspace.
- [Implement chat with create chat completion](https://docs.retellai.com/deploy/create-chat-completion.md): Step-by-step guide to implementing chat functionality with a Retell chat agent using the create chat completion API for web and SMS channels.
- [Retell Website Widget](https://docs.retellai.com/deploy/chat-widget.md): Embed the Retell website widget on your site with a single script tag — supports chat, voice, and callback modes powered by your chat and voice agents.
- [Enable SMS](https://docs.retellai.com/deploy/enable-sms.md): Enable SMS on Retell with Twilio numbers to send messages during calls, receive texts and MMS mid-call, and run two-way text conversations with chat agents.
- [SMS campaign application](https://docs.retellai.com/deploy/sms-campaign-application.md): Fill out the A2P 10DLC SMS campaign application for a Retell AI number: use case, description, opt-in flow, and sample messages that meet carrier requirements.
- [Set up versioning and tags for agents](https://docs.retellai.com/agent/version.md): Use Retell agent versions and environment tags to lock in production configurations, track change history, and roll back drafts without breaking live calls.
- [Compare agent versions](https://docs.retellai.com/agent/version-comparison.md): Compare any two versions of a Retell agent side by side to review prompt, voice, tool, and flow changes before publishing or auditing past modifications.
- [Create and schedule batch calls](https://docs.retellai.com/deploy/make-batch-call.md): Create, schedule, and monitor Retell batch calls in bulk to run outbound campaigns, send updates, or contact large recipient lists from a single workflow.
- [Spam likely overview](https://docs.retellai.com/build/telephony/call_efficiency_overview.md): Why phone numbers get marked "Spam Likely" by carriers and how Retell verified phone numbers and branded call services raise pickup rates on outbound calls.
- [Add a business profile](https://docs.retellai.com/build/telephony/business-profile.md): Set up and verify a Retell business profile before applying for verified phone numbers or branded calling, with required company information and documents.
- [Apply for verified phone number](https://docs.retellai.com/build/telephony/verified-phone.md): Apply for a Retell verified phone number on US numbers to remove "Spam Likely" labels, increase trust with carriers, and improve outbound call pickup rates.
- [Apply for branded call](https://docs.retellai.com/build/telephony/branded-call.md): Apply for Retell branded calling on US numbers so callers see your business name instead of a phone number — boost answer rates and reduce "Spam Likely".
- [Handle application rejection](https://docs.retellai.com/build/telephony/branded-call-rejection.md): Resolve rejected business profile, verified phone, and branded call applications on Retell — check rejection reasons in the dashboard and resubmit.
- [Stop caller ID service](https://docs.retellai.com/build/telephony/delete-service.md): Stop active Retell caller-ID services — branded calls and verified phone numbers — without interrupting your underlying telephony or live agent calls.
- [Make a web call](https://docs.retellai.com/deploy/web-call.md): Make browser voice calls with Retell AI: use the JavaScript SDK to connect users to an agent, control microphone audio, and handle transcripts and call events.
- [Understand concurrency & limits](https://docs.retellai.com/deploy/concurrency.md): Understand Retell concurrency and rate limits: max simultaneous calls, calls per second, burst mode, and per-workspace quota increases.
- [Call & chat history](https://docs.retellai.com/features/session-history.md): Browse Retell call and chat history in the dashboard: filter sessions, inspect transcripts and analysis, rerun analysis, and export to CSV.
- [Contacts](https://docs.retellai.com/features/contacts.md): Manage the people your Retell agents call and text: contact records keyed by phone number, custom contact fields, post-call data mappings, and CRM sync.
- [Monitor live calls](https://docs.retellai.com/features/live-monitoring.md): Watch ongoing Retell calls live: follow the transcript, listen in silently, take over from the agent, or end the call, from the dashboard or the Web SDK.
- [Analytics dashboard](https://docs.retellai.com/features/analytics-dashboard.md): Build custom Retell analytics dashboards to track call and chat metrics like success rate, latency, cost, and concurrency, with charts, filters, and breakdowns.
- [Alert rules for call and chat metrics](https://docs.retellai.com/features/alerting-overview.md): Create Retell AI alert rules that email or webhook you when call or chat volume, success rate, cost, latency, or API errors cross a threshold you set.
- [Retell webhooks overview](https://docs.retellai.com/features/webhook-overview.md): Overview of Retell webhooks — call_started, call_ended, and call_analyzed events delivered to your server so you can react to call activity without polling.
- [Register and set up a Retell webhook](https://docs.retellai.com/features/register-webhook.md): Register a Retell webhook to receive real-time call_started, call_ended, and call_analyzed events, with Node.js, Python, and signature verification code.
- [Secure the webhook](https://docs.retellai.com/features/secure-webhook.md): Verify Retell AI webhook signatures with the raw request body, X-Retell-Signature header, API key, SDK helpers, and IP allowlisting.
- [Post Call Extraction overview and categories](https://docs.retellai.com/features/post-call-analysis-overview.md): Retell Post Call Extraction automatically scores and structures customer calls after they end — built-in categories plus custom analysis for your workflow.
- [Define the information you want to extract](https://docs.retellai.com/features/post-call-analysis-create.md): Define Retell Post Call Extraction fields with boolean, selector, text, and number categories to automatically extract structured data from every call.
- [Consume the analysis data](https://docs.retellai.com/features/post-call-analysis-consumption.md): Read Retell Post Call Extraction results from the dashboard, the call_analyzed webhook, or the Get Call API, and feed them into your CRM or reports.
- [Rerun Post Call/Chat Extraction](https://docs.retellai.com/features/rerun-call-analysis.md): Edit Retell Post Call or Post Chat Extraction prompts and rerun processing on past sessions to regenerate summaries and success metrics with new criteria.
- [Automatically evaluate call quality with AI QA](https://docs.retellai.com/ai-qa/overview.md): AI QA scores Retell calls on hallucination, knowledge base accuracy, latency, sentiment, and tool usage to surface quality trends and issues.
- [Access AI QA](https://docs.retellai.com/ai-qa/get-started.md): Get started with Retell AI QA: open the AI QA tab from the sidebar and click Create QA to launch your first automated call quality evaluation.
- [Define a QA cohort](https://docs.retellai.com/ai-qa/create-cohort.md): Define a Retell AI QA cohort: pick agents, date range, and call filters, then set a sampling rate to control evaluation volume and cost.
- [Define resolution criteria](https://docs.retellai.com/ai-qa/define-resolution-criteria.md): Define resolution criteria for an AI QA cohort using AI-evaluated conditions and performance metric thresholds to decide whether each call counts as successful.
- [View QA results](https://docs.retellai.com/ai-qa/view-qa-results.md): Read your Retell AI QA results: review aggregate metrics and trends, drill into individual calls, inspect transcripts with QA diagnostics, and calibrate scores.
- [AI QA metrics](https://docs.retellai.com/ai-qa/terminologies.md): Reference for every AI QA metric and term — average latency, hallucination rate, KB accuracy, overlapping speech, sentiment — and how each one is evaluated.
- [Address metric issues](https://docs.retellai.com/ai-qa/address-metric-issues.md): Step-by-step fixes for common AI QA metric issues — hallucinations, knowledge base mistakes, overlapping speech, latency, sentiment, and tool errors.
- [Reliability Overview](https://docs.retellai.com/reliability/reliability-overview.md): How Retell AI maintains 99.9% uptime with enterprise infrastructure, monitoring, fallback mechanisms, and platform resilience features.
- [Check estimated latency](https://docs.retellai.com/reliability/check-estimated-latency.md): View estimated end-to-end latency for a Retell agent before going live — see which turtle-icon features are pushing latency higher than expected.
- [Check actual latency](https://docs.retellai.com/reliability/check-actual-latency.md): Monitor per-call latency in the Retell Call History dashboard or via the Get Call API — review P50, P90, and P99 end-to-end latency to find slow calls.
- [Troubleshoot high latency](https://docs.retellai.com/reliability/troubleshoot-latency.md): Reduce high Retell end-to-end latency — pick a faster LLM, shorten your prompt, enable fast tier, and diagnose slow LLM, ASR, and TTS components per call.
- [Increase transcription accuracy](https://docs.retellai.com/reliability/wrong-transcript.md): Increase Retell transcription accuracy — use boosted keywords for niche terms, choose the right ASR provider, and tune transcription modes for clarity.
- [Debug wrong response](https://docs.retellai.com/reliability/wrong-response.md): Fix Retell agents that give incorrect responses — switch to a more capable LLM, simplify prompt structure, add finetune examples, and review function calls.
- [Debug call transfer failure](https://docs.retellai.com/reliability/call-performance.md): Debug Retell call transfer failures — verify the `transfer_call` function is configured correctly for single, multi-prompt, and conversation flow agents.
- [Debug call disconnection](https://docs.retellai.com/reliability/debug-call-disconnect.md): Diagnose why a Retell call disconnected — look up the `disconnection_reason` in the dashboard or Get Call API and follow the table of causes and fixes.
- [Debug outbound connection issues](https://docs.retellai.com/reliability/debug-outbound-call.md): Diagnose `not_connected` outbound Retell calls — work through `invalid_destination`, `no_valid_payment`, carrier blocks, and other disconnection reasons.
- [Debug SIP calls using PCAP file](https://docs.retellai.com/reliability/debug-calls-pcap.md): Capture and analyze PCAP files in Wireshark and tshark to diagnose Retell SIP calls — codec negotiation, audio quality, one-way audio, and missed DTMF tones.
- [Prevent abuse](https://docs.retellai.com/reliability/prevent-abuse.md): Defend Retell agents against International Revenue Sharing Fraud and other abuse — rate limit traffic, restrict destinations, and lock down public keys.
- [Fraud Protection](https://docs.retellai.com/reliability/fraud-protection.md): Protect your Retell deployment with rate limiting by IP and destination number, geographic restrictions, and public key fraud protection for frontend traffic.
- [Create and manage Retell workspaces](https://docs.retellai.com/accounts/workspace.md): Create and manage Retell workspaces, find your workspace ID, invite teammates to collaborate, switch between workspaces, and safely delete a workspace.
- [Manage your Retell AI account](https://docs.retellai.com/accounts/account.md): Check account status, reset your password, change your email address, switch to Google SSO, stop charges, and delete your Retell AI account.
- [Access Control](https://docs.retellai.com/accounts/access-control.md): Manage your Retell workspace with role-based access control: invite members, assign Admin, Developer, Analyst, or Viewer roles, and control permissions.
- [KYC Verification](https://docs.retellai.com/accounts/kyc.md): Complete KYC verification — automatic, Persona-based, or manual review — to unlock outbound calling, phone number purchases, and SMS on your Retell account.
- [Retell AI billing: credits, auto recharge, and invoices](https://docs.retellai.com/accounts/billing.md): How Retell billing works: prepaid credits and auto recharge on credit-based accounts, legacy end-of-month billing, usage tracking, and invoices.
- [Exceptions to Our Per-Minute Pricing](https://docs.retellai.com/accounts/billing-exceptions.md): Billing adjustments that may affect Retell call costs: 10-second minimum for dynamic opening messages and extra charges for long prompt token counts.
- [Add payment methods](https://docs.retellai.com/accounts/add-payment.md): Add a Stripe payment method to your Retell workspace to buy credits, keep calling after the free trial, purchase phone numbers, and avoid service interruptions.
- [Handle failed payments](https://docs.retellai.com/accounts/fail-payment.md): Resolve failed Retell payments: contact your bank to allowlist transactions, request written confirmation, and update your payment method on Stripe.
- [API Key Overview](https://docs.retellai.com/accounts/api-keys-overview.md): How API keys authenticate your Retell REST API requests, SDK integrations, and webhook endpoints, plus best practices for storing and rotating keys safely.
- [Manage API keys and permission scopes](https://docs.retellai.com/accounts/manage-api-keys.md): Create, delete, and rotate Retell API keys, set a webhook signing key, and restrict permissions with read or edit scopes for Build, Monitor, and Deploy.
- [Public keys](https://docs.retellai.com/accounts/public-keys.md): Use Retell AI public keys for web calls and the website widget: authenticate browser requests, restrict allowed domains, and configure reCAPTCHA protection.
- [Data Storage Settings](https://docs.retellai.com/accounts/privacy-disable.md): Control how Retell stores sensitive call data — recordings, transcripts, dynamic variables, caller IDs, KB logs — with per-agent privacy settings.
- [Data Retention Policy](https://docs.retellai.com/accounts/data-retention.md): Configure per-agent data retention to automatically delete call and chat data — transcripts, recordings, and logs — after a set period for compliance.
- [Opt in to secure URL](https://docs.retellai.com/accounts/signed-secure-url.md): Opt in to secure URLs so Retell-generated call recording and log links automatically expire after 24 hours, preventing unauthorized access if a link leaks.
- [Security and compliance](https://docs.retellai.com/general/compliance.md): Retell AI is HIPAA and GDPR compliant and SOC 2 Type 1 and Type 2 certified. Review our data handling, BAA, DPA, and GDPR erasure process.
- [Integrations overview](https://docs.retellai.com/integrations/overview.md): Connect HubSpot, Salesforce, Zendesk, Google Drive, Notion, Calendly, and more to Retell AI for agent tools, contact sync, and knowledge base sync.
- [CRM integrations](https://docs.retellai.com/integrations/crm-overview.md): Connect Salesforce, HubSpot, Dynamics 365, GoHighLevel, or Zoho to Retell AI: sync contacts both ways, map analysis to fields, and log conversations.
- [CRM data mappings](https://docs.retellai.com/integrations/crm-mappings.md): How data flows between your CRM, Retell AI contacts, and Post Call Extraction: inbound and outbound field mappings, update modes, and custom fields.
- [Give your AI agent persistent contact memory](https://docs.retellai.com/integrations/build-contact-memory.md): Map Post Call Extraction fields to contact fields so your Retell AI agent remembers preferences, past issues, and commitments across every conversation.
- [Connect HubSpot](https://docs.retellai.com/integrations/hubspot.md): Connect HubSpot to Retell AI with a private app access token: the scopes to grant, where the token lives, and how to verify the connection works.
- [HubSpot contact sync](https://docs.retellai.com/integrations/hubspot-contact-sync.md): Sync HubSpot contacts with Retell AI: field mappings, Post Call Extraction write-back, and call and chat logging on the contact activity timeline.
- [HubSpot agent functions](https://docs.retellai.com/integrations/hubspot-functions.md): HubSpot tools for Retell AI agents: look up and update contacts, work deals and companies, create tasks and notes, and log calls to the timeline.
- [Connect Salesforce](https://docs.retellai.com/integrations/salesforce.md): Connect Salesforce to Retell AI with an External Client App: OAuth client credentials, the Run As user setup, and how to verify the connection works.
- [Salesforce contact sync](https://docs.retellai.com/integrations/salesforce-contact-sync.md): Sync Salesforce Contacts with Retell AI: phone-matched field mappings, Post Call Extraction write-back, and calls and chats logged as Salesforce Tasks.
- [Salesforce agent functions](https://docs.retellai.com/integrations/salesforce-functions.md): Salesforce tools for Retell AI agents: identify callers, read opportunities and cases, create contacts, leads, and tasks, run SOQL queries, and update records.
- [Connect Dynamics 365](https://docs.retellai.com/integrations/microsoft-dynamics.md): Connect Microsoft Dynamics 365 to Retell AI with OAuth: find your Dataverse environment URL, sign in with Microsoft, and verify the connection works.
- [Dynamics 365 contact sync](https://docs.retellai.com/integrations/microsoft-dynamics-contact-sync.md): Sync Microsoft Dynamics 365 Contacts with Retell AI: field mappings, Post Call Extraction write-back, and calls logged as Phone Call activities.
- [Dynamics 365 agent functions](https://docs.retellai.com/integrations/microsoft-dynamics-functions.md): Dynamics 365 tools for Retell AI agents: look up and update Contacts, create Tasks and Notes, and log calls as completed Phone Call activities.
- [Connect GoHighLevel](https://docs.retellai.com/integrations/gohighlevel.md): Connect GoHighLevel to Retell AI with a Private Integration token and Location ID: the scopes to grant, where each value lives, and how to verify.
- [GoHighLevel contact sync](https://docs.retellai.com/integrations/gohighlevel-contact-sync.md): Sync GoHighLevel sub-account contacts with Retell AI: field mappings, Post Call Extraction write-back, and conversation logging as contact notes.
- [GoHighLevel agent functions](https://docs.retellai.com/integrations/gohighlevel-functions.md): GoHighLevel tools for Retell AI agents: look up and update contacts, add tags, work opportunities and tasks, and book the sub-account's calendars.
- [Connect Zoho CRM](https://docs.retellai.com/integrations/zoho.md): Connect Zoho CRM to Retell AI with one OAuth sign-in: Retell detects your Zoho data center, then syncs contacts and runs agent tools on your records.
- [Zoho contact sync](https://docs.retellai.com/integrations/zoho-contact-sync.md): Sync Zoho CRM Contacts with Retell AI: field mappings, Post Call Extraction write-back, and every call logged as a Zoho Call record on the timeline.
- [Zoho agent functions](https://docs.retellai.com/integrations/zoho-functions.md): Zoho CRM tools for Retell AI agents: identify the caller, read their Deals, update Contacts, and create Tasks, Notes, and Call records on the timeline.
- [Connect Zendesk](https://docs.retellai.com/integrations/zendesk.md): Connect Zendesk to Retell AI with OAuth so agents can identify callers, look up their tickets, file new ones, and add comments or private notes.
- [Zendesk agent functions](https://docs.retellai.com/integrations/zendesk-functions.md): Zendesk tools for Retell AI agents: identify callers by phone, read and update their tickets, create new ones, and add public comments or private notes.
- [Connect Google Drive](https://docs.retellai.com/integrations/google-drive.md): Connect Google Drive to Retell AI with one OAuth sign-in. The drive.file scope grants per-file access only, so agents answer from files you pick.
- [Google Drive knowledge base sync](https://docs.retellai.com/integrations/google-drive-knowledge-base.md): Sync Google Drive files into a Retell AI knowledge base: pick Docs and Sheets once, and changed files re-sync automatically on a 24-hour refresh cycle.
- [Connect OneDrive](https://docs.retellai.com/integrations/microsoft-onedrive.md): Connect Microsoft OneDrive to Retell AI with a read-only Microsoft sign-in, then sync OneDrive files into knowledge bases your agent answers from.
- [OneDrive knowledge base sync](https://docs.retellai.com/integrations/microsoft-onedrive-knowledge-base.md): Sync Microsoft OneDrive files into a Retell AI knowledge base: pick files in Microsoft's file picker, and changed files re-sync every 24 hours.
- [Connect Notion](https://docs.retellai.com/integrations/notion.md): Connect Notion to Retell AI with an API key: create an internal connection, share pages with it, and sync them into knowledge bases your agent answers from.
- [Notion knowledge base sync](https://docs.retellai.com/integrations/notion-knowledge-base.md): Sync Notion pages into a Retell AI knowledge base: pick the pages shared with your connection, and edited pages re-sync automatically every 24 hours.
- [GoHighLevel agent functions](https://docs.retellai.com/integrations/gohighlevel-functions.md): GoHighLevel tools for Retell AI agents: look up and update contacts, add tags, work opportunities and tasks, and book the sub-account's calendars.
- [Connect Calendly](https://docs.retellai.com/integrations/calendly.md): Connect Calendly to Retell AI with a personal access token so agents can check availability, book appointments, and cancel scheduled events.
- [Calendly agent functions](https://docs.retellai.com/integrations/calendly-functions.md): Calendly tools for Retell AI agents: check real availability, book appointments, and look up or cancel scheduled events live during the call.
- [Connect Cal.com](https://docs.retellai.com/integrations/cal-com.md): Connect Cal.com to Retell AI with an API key: create a never-expiring key, pick the cal.com or cal.eu domain, and verify the workspace connection.
- [Cal.com agent functions](https://docs.retellai.com/integrations/cal-com-functions.md): Cal.com tools for Retell AI agents: check live availability, book appointments, and list, get, reschedule, or cancel bookings during the call.
- [Trigger Retell calls from HubSpot workflows](https://docs.retellai.com/integrations/hubspot-marketplace.md): Install and configure the Retell AI HubSpot app to trigger outbound voice agent calls from HubSpot workflows, pass contact context, and sync call results back.
- [Trigger Retell calls from Zoho CRM workflows](https://docs.retellai.com/integrations/zoho-marketplace.md): Install the Retell AI Zoho CRM extension to trigger outbound voice agent calls from workflow rules and write summaries, results, and recordings back.
- [Custom LLM overview](https://docs.retellai.com/integrate-llm/overview.md): Run your own LLM behind a Retell voice agent. Retell handles telephony, transcription, and turn-taking while your WebSocket server generates each reply.
- [Set up a custom LLM WebSocket server for your Retell agent](https://docs.retellai.com/integrate-llm/setup-websocket-server.md): Build the LLM WebSocket server that a Retell custom LLM agent connects to: handle config and begin messages, respond to response_required events.
- [Connect your LLM](https://docs.retellai.com/integrate-llm/integrate-llm.md): Stream LLM completions to a Retell voice agent over the LLM WebSocket, build prompts from the live transcript, and cancel responses Retell discards.
- [Add function calling](https://docs.retellai.com/integrate-llm/integrate-function-calling.md): Give a Retell custom LLM agent tools to book appointments, transfer to a human, press IVR digits, and end calls, all logged in the transcript.
- [Troubleshooting](https://docs.retellai.com/integrate-llm/troubleshooting.md): Debug a Retell custom LLM integration: map error_llm_websocket disconnection reasons to fixes for silent agents, dropped calls, and WebSocket errors.
- [Best practices](https://docs.retellai.com/integrate-llm/llm-best-practice.md): Keep a Retell custom LLM agent fast and reliable: cut time to first sentence, write prompts for speech, control tool accuracy, and survive dropped connections.
- [Audio Basics](https://docs.retellai.com/knowledge/audio-basics.md): Audio fundamentals for building voice AI — sampling, quantization, codecs, sample rates, and how audio is represented digitally in telephony systems.
- [Retell AI API Reference](https://docs.retellai.com/api-references/overview.md): Reference for the Retell AI API: authentication, base URL, SDKs, and endpoints for building and managing voice and chat agents programmatically.
- [Create Phone Call](https://docs.retellai.com/api-references/create-phone-call.md): Create a new outbound phone call
- [Create Web Call](https://docs.retellai.com/api-references/create-web-call.md): Create a new web call and return browser connection details.
- [Get Call](https://docs.retellai.com/api-references/get-call.md): Retrieve details of a specific call
- [List Calls](https://docs.retellai.com/api-references/list-calls.md): List calls with unified cursor pagination response.
- [Update Call](https://docs.retellai.com/api-references/update-call.md): Update metadata and sensitive data storage settings for an existing call.
- [Update Live Call](https://docs.retellai.com/api-references/update-live-call.md): Update an ongoing call at runtime. Supports overriding dynamic variables, metadata, and the data storage setting on the running call, and controlling the live agent (inject context, trigger a response). These overrides take effect immediately on the live call; metadata and data storage setting chang…
- [Monitor Call WebSocket](https://docs.retellai.com/api-references/monitor-call-websocket.md): Stream a live call transcript, tool calls, and node transitions from the Retell AI monitor call WebSocket using an API key or public key.
- [Rerun Call Analysis](https://docs.retellai.com/api-references/rerun-call-analysis.md): Rerun post-call analysis for a specific call. This operation incurs charges.
- [Stop Call](https://docs.retellai.com/api-references/stop-call.md): Stop an ongoing call.
- [Delete Call](https://docs.retellai.com/api-references/delete-call.md): Delete a specific call and its associated data
- [Create Chat](https://docs.retellai.com/api-references/create-chat.md): Create a chat session
- [Create Outbound SMS](https://docs.retellai.com/api-references/create-sms-chat.md): Start an outbound SMS chat conversation with a phone number using the specified agent. The agent must be configured for chat mode. The initial SMS message will be automatically generated and sent based on the agent's configuration.
- [Get Chat](https://docs.retellai.com/api-references/get-chat.md): Retrieve details of a specific chat
- [Create Chat Completion](https://docs.retellai.com/api-references/create-chat-completion.md): Create a chat completion message
- [List Chats](https://docs.retellai.com/api-references/list-chats.md): List chats with unified cursor pagination response.
- [Update Chat](https://docs.retellai.com/api-references/update-chat.md): Update metadata and sensitive data storage settings for an existing chat.
- [Rerun Chat Analysis](https://docs.retellai.com/api-references/rerun-chat-analysis.md): Rerun post-chat analysis for a specific chat. This operation incurs charges.
- [End Chat](https://docs.retellai.com/api-references/end-chat.md): End an ongoing chat
- [Delete Chat](https://docs.retellai.com/api-references/delete-chat.md): Delete an existing chat
- [Agent Playground Completion](https://docs.retellai.com/api-references/agent-playground-completion.md): Stateless playground completion. Send the full conversation history (same shape as chat completion messages) and receive only the newly generated messages. Nothing is persisted server-side — the caller manages conversation state.
- [Create Phone Number](https://docs.retellai.com/api-references/create-phone-number.md): Buy a new phone number & Bind agents
- [Get Phone Number](https://docs.retellai.com/api-references/get-phone-number.md): Retrieve details of a specific phone number
- [List Phone Numbers](https://docs.retellai.com/api-references/list-phone-numbers.md): List phone numbers with pagination
- [Update Phone Number](https://docs.retellai.com/api-references/update-phone-number.md): Update agent bound to a purchased phone number
- [Delete Phone Number](https://docs.retellai.com/api-references/delete-phone-number.md): Delete an existing phone number
- [Create Voice Agent](https://docs.retellai.com/api-references/create-agent.md): Create a new agent
- [Get Voice Agent](https://docs.retellai.com/api-references/get-agent.md): Retrieve details of a specific agent
- [List Voice Agents](https://docs.retellai.com/api-references/list-agents.md): List unique agents with pagination.
- [Update Voice Agent](https://docs.retellai.com/api-references/update-agent.md): Update an existing agent's latest draft version
- [Delete Agent](https://docs.retellai.com/api-references/delete-agent.md): Delete an existing agent
- [Publish Agent](https://docs.retellai.com/api-references/publish-agent.md): Publish an existing draft version in place.
- [Create Draft Agent Version](https://docs.retellai.com/api-references/create-agent-version.md): Create a new draft agent version from a base version.
- [Delete Agent Version](https://docs.retellai.com/api-references/delete-agent-version.md): Delete a specific agent version.
- [List Agent Versions](https://docs.retellai.com/api-references/list-agent-versions.md): List stored versions of a voice or chat agent with pagination.
- [Create Chat Agent](https://docs.retellai.com/api-references/create-chat-agent.md): Create a new chat agent
- [Get Chat Agent](https://docs.retellai.com/api-references/get-chat-agent.md): Retrieve details of a specific chat agent
- [List Chat Agents](https://docs.retellai.com/api-references/list-chat-agents.md): List unique agents with pagination.
- [Update Chat Agent](https://docs.retellai.com/api-references/update-chat-agent.md): Update an existing chat agent
- [Delete Chat Agent](https://docs.retellai.com/api-references/delete-chat-agent.md): Delete an existing chat agent
- [Publish Chat Agent](https://docs.retellai.com/api-references/publish-chat-agent.md): Publish an existing draft version in place.
- [Create Draft Chat Agent Version](https://docs.retellai.com/api-references/create-chat-agent-version.md): Create a new draft agent version from a base version.
- [Delete Chat Agent Version](https://docs.retellai.com/api-references/delete-chat-agent-version.md): Delete a specific agent version.
- [List Agent Versions](https://docs.retellai.com/api-references/list-agent-versions.md): List stored versions of a voice or chat agent with pagination.
- [Create Retell LLM](https://docs.retellai.com/api-references/create-retell-llm.md): Create a new Retell LLM Response Engine that can be attached to an agent. This is used to generate response output for the agent.
- [Get Retell LLM](https://docs.retellai.com/api-references/get-retell-llm.md): Retrieve details of a specific Retell LLM Response Engine
- [List Retell LLMs](https://docs.retellai.com/api-references/list-retell-llms.md): List Retell LLM Response Engines with pagination
- [Update Retell LLM](https://docs.retellai.com/api-references/update-retell-llm.md): Update an existing Retell LLM Response Engine
- [Delete Retell LLM](https://docs.retellai.com/api-references/delete-retell-llm.md): Delete an existing Retell LLM Response Engine
- [Create Conversation Flow](https://docs.retellai.com/api-references/create-conversation-flow.md): Create a new Conversation Flow that can be attached to an agent. This is used to generate response output for the agent.
- [Get Conversation Flow](https://docs.retellai.com/api-references/get-conversation-flow.md): Retrieve details of a specific Conversation Flow
- [List Conversation Flows](https://docs.retellai.com/api-references/list-conversation-flows.md): List conversation flows with pagination
- [Update Conversation Flow](https://docs.retellai.com/api-references/update-conversation-flow.md): Update an existing conversation flow
- [Delete Conversation Flow](https://docs.retellai.com/api-references/delete-conversation-flow.md): Delete a conversation flow and all its versions
- [Create Conversation Flow Subflow](https://docs.retellai.com/api-references/create-conversation-flow-component.md): Create a new shared conversation flow component
- [Get Conversation Flow Subflow](https://docs.retellai.com/api-references/get-conversation-flow-component.md): Get a shared conversation flow component
- [List Conversation Flow Subflows](https://docs.retellai.com/api-references/list-conversation-flow-components.md): List shared conversation flow components with pagination
- [Update Conversation Flow Subflow](https://docs.retellai.com/api-references/update-conversation-flow-component.md): Update an existing shared conversation flow component
- [Delete Conversation Flow Subflow](https://docs.retellai.com/api-references/delete-conversation-flow-component.md): Delete a shared conversation flow component. When deleting a shared component, creates local copies for all linked conversation flows.
- [Get MCP Tools](https://docs.retellai.com/api-references/get-mcp-tools.md): Get MCP tools for a specific agent
- [Create Knowledge Base](https://docs.retellai.com/api-references/create-knowledge-base.md): Create a new knowledge base
- [Get Knowledge Base](https://docs.retellai.com/api-references/get-knowledge-base.md): Retrieve details of a specific knowledge base
- [List Knowledge Bases](https://docs.retellai.com/api-references/list-knowledge-bases.md): List all knowledge bases
- [Delete Knowledge Base](https://docs.retellai.com/api-references/delete-knowledge-base.md): Delete an existing knowledge base
- [Add Knowledge Base Sources](https://docs.retellai.com/api-references/add-knowledge-base-sources.md): Add sources to a knowledge base
- [Delete Knowledge Base Source](https://docs.retellai.com/api-references/delete-knowledge-base-source.md): Delete an existing source from knowledge base
- [Add Voice](https://docs.retellai.com/api-references/add-voice.md): Add a community voice to the voice library
- [Clone Voice](https://docs.retellai.com/api-references/clone-voice.md): Clone a voice from audio files
- [Search Voice](https://docs.retellai.com/api-references/search-voice.md): Search for community voices from voice providers
- [Get Voice](https://docs.retellai.com/api-references/get-voice.md): Retrieve details of a specific voice
- [List Voices](https://docs.retellai.com/api-references/list-voices.md): List all voices available to the user
- [Create Batch Call](https://docs.retellai.com/api-references/create-batch-call.md): Create a batch call
- [Create Contact](https://docs.retellai.com/api-references/create-contact.md): Create a new contact.
- [Get Contact](https://docs.retellai.com/api-references/get-contact.md): Retrieve a contact by ID.
- [Get Contact by Phone](https://docs.retellai.com/api-references/get-contact-by-phone.md): Retrieve a contact by phone number. At most one contact exists per phone number in an organization.
- [List Contacts](https://docs.retellai.com/api-references/list-contacts.md): List contacts, newest conversation first by default, with the total count of matches alongside the page. Page through results with `pagination_key`; `skip` is available for offset-style paging but is slower on large contact sets and can repeat or miss rows as contacts are updated.
- [List Contact Conversations](https://docs.retellai.com/api-references/list-contact-conversations.md): List a contact's conversations (inbound calls, outbound calls, and chats) merged into a single timeline, most recent first. Results are matched by the contact's phone number. Use the returned `pagination_key` to fetch the next page.
- [Update Contact](https://docs.retellai.com/api-references/update-contact.md): Update an existing contact.
- [Delete Contact](https://docs.retellai.com/api-references/delete-contact.md): Delete a contact. A contact linked to a record in a connected CRM cannot be deleted while two-way sync is active — unlink the CRM app first, otherwise the next sync would recreate it.
- [Backfill Contact Analysis Data](https://docs.retellai.com/api-references/backfill-contact-analysis-data.md): Start a job that populates contact analysis attributes on existing Retell calls, filtered by agent and start timestamp, returning a job status.
- [Get Backfill Job Status](https://docs.retellai.com/api-references/get-backfill-contact-job-status.md): Get the status of the contact analysis data backfill job.
- [Create App](https://docs.retellai.com/api-references/create-app.md): Create an App: the connection to one external system (a CRM, calendar, support desk, and so on), holding its credentials and settings. Providers with caller-managed credentials accept auth_config. Providers using the OAuth callback must omit auth_config and be authorized through connect-app. Credent…
- [Get App](https://docs.retellai.com/api-references/get-app.md): Get an App by id.
- [List Apps](https://docs.retellai.com/api-references/list-apps.md): List Apps in the organization (paginated).
- [Update App](https://docs.retellai.com/api-references/update-app.md): Partially update an App. Omitted fields remain unchanged. Updating auth_config or tenant metadata invalidates the cached provider token immediately. Providers using the OAuth callback reject auth_config and must be reauthorized through connect-app.
- [Delete App](https://docs.retellai.com/api-references/delete-app.md): Delete an App. Fails when agents or knowledge bases still reference it, unless force_delete is set. If a CRM config is linked to this App, the link is cleared.
- [List App Usages](https://docs.retellai.com/api-references/list-app-usages.md): List the agents and knowledge bases referencing an App, most recently configured first by default.
- [Test App Auth](https://docs.retellai.com/api-references/test-app-auth.md): Probe the App's stored credentials by making a minimal authenticated call to the provider. Returns success=true on a successful round-trip, and records the outcome on the App's connection_status either way.
- [Get CRM Config](https://docs.retellai.com/api-references/get-crm-config.md): Get the organization's CRM configuration: which CRM app is linked, the custom contact fields defined for it, and how post-call analysis data is written back to contacts. Returns an empty configuration when nothing has been set up yet.
- [Update CRM Config](https://docs.retellai.com/api-references/update-crm-config.md): Update the organization's CRM configuration. Omitted fields stay as they are; a field that is sent replaces its stored value in full.
- [Get CRM Schema](https://docs.retellai.com/api-references/get-crm-schema.md): Get the contact schema of the connected CRM: the fields available on its contact object, which are the values that sync mappings can reference.
- [Run Sync Job](https://docs.retellai.com/api-references/run-sync-job.md): Start a contact sync with the linked CRM app immediately, instead of waiting for the scheduled sync. One sync runs per organization at a time: starting another while one is in flight is rejected. Poll get-sync-job-status for progress.
- [Get Sync Job Status](https://docs.retellai.com/api-references/get-sync-job-status.md): Get the status of the organization's contact sync, whether it was started manually or by the schedule. Returns status `idle` when no sync is running.
- [Create Test Case Definition](https://docs.retellai.com/api-references/create-test-case-definition.md): Create a new test case definition
- [Get Test Case Definition](https://docs.retellai.com/api-references/get-test-case-definition.md): Get a test case definition by ID
- [List Test Case Definitions](https://docs.retellai.com/api-references/list-test-case-definitions.md): List test case definitions with pagination
- [Update Test Case Definition](https://docs.retellai.com/api-references/update-test-case-definition.md): Update a test case definition
- [Delete Test Case Definition](https://docs.retellai.com/api-references/delete-test-case-definition.md): Delete a test case definition
- [Create Batch Test](https://docs.retellai.com/api-references/create-batch-test.md): Create a batch test to run multiple test cases
- [Get Batch Test](https://docs.retellai.com/api-references/get-batch-test.md): Get a batch test job by ID
- [List Batch Tests](https://docs.retellai.com/api-references/list-batch-tests.md): List batch test jobs with pagination
- [Get Test Run](https://docs.retellai.com/api-references/get-test-run.md): Get a test case job (test run) by ID
- [List Test Runs](https://docs.retellai.com/api-references/list-test-runs.md): List test case jobs (test runs) for a batch test job with pagination
- [Get Concurrency](https://docs.retellai.com/api-references/get-concurrency.md): Get the current concurrency and concurrency limit of the org
- [List Export Requests](https://docs.retellai.com/api-references/list-export-requests.md): List export requests with pagination
- [Import Phone Number](https://docs.retellai.com/api-references/import-phone-number.md): Import a phone number from custom telephony & Bind agents
- [Register Phone Call](https://docs.retellai.com/api-references/register-phone-call.md): Register a new phone call for custom telephony
- [LLM WebSocket](https://docs.retellai.com/api-references/llm-websocket.md): LLM WebSocket protocol for streaming requests from Retell to your custom LLM server and returning responses, tool calls, and DTMF actions during a live call.
- [Retell SDKs for TypeScript and Python](https://docs.retellai.com/get-started/sdk.md): Official Retell SDKs for Node.js and Python. Typed clients with API key auth, structured errors, and full voice and chat endpoint coverage.
- [Create voice agent with TypeScript SDK](https://docs.retellai.com/get-started/create-agent-with-sdk.md): Create a Retell AI phone agent with the TypeScript SDK in Node.js: configure its prompt, voice, webhook, call limits, testing, and published version.
- [Retell MCP server for AI assistants](https://docs.retellai.com/get-started/mcp-server.md): Use Retell's MCP server to build and manage voice agents from MCP-capable clients like Cursor, Claude Desktop, and Claude Code via Retell APIs.
- [Retell CLI](https://docs.retellai.com/get-started/cli.md): Install the Retell CLI to manage agents, phone numbers, knowledge bases, and other Retell resources from your terminal with simple commands.
- [Retell deprecations and breaking changes](https://docs.retellai.com/deprecation-notice/overview.md): Browse upcoming and past Retell API and SDK deprecations and breaking changes by date. Subscribe via RSS for new deprecation notices.
- [Legacy browser JavaScript SDK (09/30/2026)](https://docs.retellai.com/deprecation-notice/2026/09-30_create_web_call_v2.md): Migrate from the deprecated Retell AI browser client SDK v2 to v3: replace RetellWebClient with RetellClient and update call creation and event handlers.
- [Legacy SIP endpoint removed (09/30/2026)](https://docs.retellai.com/deprecation-notice/2026/09-30_sip_legacy_endpoint.md): Retell retires SIP endpoint sip:5t4n6j0wnrl.sip.livekit.cloud on 09/30/2026; migrate elastic trunks and dial-to-sip integrations to sip:sip.retellai.com.
- [Cal.com built-in tools (09/30–10/31/2026)](https://docs.retellai.com/deprecation-notice/2026/10-31_legacy_calcom_tools.md): Retell's built-in Cal.com tools are gone from the dashboard, frozen by the API on 09/30/2026, and migrated to the Cal.com integration on 10/31/2026.
- [Update Call restricted to ended calls (08/31/2026)](https://docs.retellai.com/deprecation-notice/2026/08-31_update_call_ended_calls_only.md): Update Call becomes ended-calls-only on 08/31/2026; override_dynamic_variables and mid-call data_storage_setting changes move to Update Live Call.
- [Cal.com built-in tools (09/30–10/31/2026)](https://docs.retellai.com/deprecation-notice/2026/10-31_legacy_calcom_tools.md): Retell's built-in Cal.com tools are gone from the dashboard, frozen by the API on 09/30/2026, and migrated to the Cal.com integration on 10/31/2026.
- [Legacy get-agent-versions endpoints removed (09/15/2026)](https://docs.retellai.com/deprecation-notice/2026/09-15_get_agent_versions.md): On 09/15/2026 Retell removes GET /get-agent-versions and GET /get-chat-agent-versions. Migrate to the unified GET /list-agent-versions endpoint.
- [Update Call restricted to ended calls (08/31/2026)](https://docs.retellai.com/deprecation-notice/2026/08-31_update_call_ended_calls_only.md): Update Call becomes ended-calls-only on 08/31/2026; override_dynamic_variables and mid-call data_storage_setting changes move to Update Live Call.
- [Multilingual agent locale array required (07/31/2026)](https://docs.retellai.com/deprecation-notice/2026/07-31_legacy_multilingual_setting.md): On 07/31/2026, the scalar "multi" value of the agent language field is removed in favor of an explicit locale array for multilingual Retell agents.
- [Legacy agent list endpoints removed (07/31/2026)](https://docs.retellai.com/deprecation-notice/2026/07-31_agent_list_endpoints.md): On 07/31/2026 Retell removes GET /list-agents and GET /list-chat-agents. Migrate to the unified POST /v2/list-agents endpoint with filters.
- [Legacy MCP server (retell.stlmcp.com) removed (07/20/2026)](https://docs.retellai.com/deprecation-notice/2026/07-20_legacy_mcp_server.md): The legacy hosted MCP server at retell.stlmcp.com shuts down on 07/20/2026. Migrate your MCP client to mcp.retellai.com — auth is unchanged.
- [Unified publish-agent-version endpoint (07/20/2026)](https://docs.retellai.com/deprecation-notice/2026/07-20_agent_version_endpoints.md): On 07/20/2026 Retell deprecates the legacy publish-agent and publish-chat-agent endpoints — migrate to the unified publish-agent-version endpoint.
- [ElevenLabs Turbo models replaced with Flash (07/12/2026)](https://docs.retellai.com/deprecation-notice/2026/07-12_elevenlabs_turbo_models.md): On 07/12/2026, Retell replaces the ElevenLabs Turbo voice models (eleven_turbo_v2 and eleven_turbo_v2_5) with the Flash equivalents at lower latency.
- [Legacy list endpoints removed for v2/v3 (06/15/2026)](https://docs.retellai.com/deprecation-notice/2026/06-15_legacy_list_endpoints.md): On 06/15/2026 Retell removes legacy list endpoints (batch tests, conversation flows, phone numbers, Retell LLMs) — migrate to versioned v2 and v3 endpoints.
- [Claude Sonnet and Gemini Flash model upgrades (05/25/2026)](https://docs.retellai.com/deprecation-notice/2026/05-25_model_replacements.md): On 05/25/2026 Retell replaces Claude 4.0 Sonnet with 4.6 Sonnet and migrates Gemini 2.0 Flash, Flash-Lite, and 2.5 Flash to the newer Gemini 3.0 and 3.1 models.
- [Conversation node tools replaced by subagent (04/18/2026)](https://docs.retellai.com/deprecation-notice/2026/04-18_conversation_node_tools.md): On 04/18/2026 Retell deprecates `tools` and `tool_ids` on conversation nodes in favor of the new subagent node for dialogue that calls tools mid-call.
- [OpenAI Realtime and Cartesia Sonic replaced (04/03/2026)](https://docs.retellai.com/deprecation-notice/2026/04-03_model_replacements.md): On 04/03/2026 Retell replaces OpenAI Realtime models (gpt-4o-realtime, gpt-4o-mini-realtime) and Cartesia Sonic-2 and Sonic-Turbo with their newer counterparts.
- [Phone number single-agent fields removed (03/31/2026)](https://docs.retellai.com/deprecation-notice/2026/03-31_phone_number_agent_fields.md): On 03/31/2026 Retell deprecates single-agent fields on phone numbers in favor of weighted inbound, outbound, and SMS agent lists across the phone number APIs.
- [Explicit cold transfer mode selection (01/23/2026)](https://docs.retellai.com/deprecation-notice/2026/01-23_cold_transfer_mode_selection.md): On 01/23/2026 the `show_transferee_as_caller` field changes meaning — Retell switches to explicit cold transfer mode between SIP REFER and SIP INVITE.

## OpenAPI Specs

- [config](/config.yaml)
- [gen](/gen.yaml)
- [openapi-final](/openapi-final.yaml)
- [openapi](/openapi.yaml)
- [package-lock](/package-lock.json)