Trigger Retell calls from Slack

Install the Retell AI Slack app to start outbound voice agent calls from Slack and post call summaries, results, and recordings back to channels.

This guide connects Retell AI to Slack so team members can start outbound calls with a slash command. After each analyzed call, Retell posts the result to the originating channel.

Before you start

• Permission to install apps in the target Slack workspace
• A Retell account with an API key, configured voice agent, and outbound phone number
• A Slack channel where Retell can post call results; invite Retell AI before using a private channel
• A valid destination number in E.164 format, such as [phone]

Use your own API key, webhook URL, agent, caller ID, channels, and test numbers. The screenshots use sample or masked values.

Install Retell AI in Slack

1. Add Retell AI to the workspace

   Open the Slack App Directory, search for Retell AI, select Add to Slack, and choose the workspace you want to connect.

   
2. Approve the requested permissions

   Review the Slack permissions, then select Allow to finish installing the app.

   

Connect Slack and configure Retell

1. Open the Retell AI App Home

   In Slack, open Apps → Retell AI → Home. If the workspace is not connected, select Connect Slack and approve access.

   
2. Launch the configuration wizard

   From App Home, select Launch configuration wizard. Sign in to Retell if required, or continue without signing in when your Retell account is already configured.

   
3. Set the webhook key

   In the Retell dashboard, go to Settings → API Keys. Copy an existing key or select Add Key to create one. Open the key’s ⋮ options menu and select Set as webhook key, then copy the key value.

   

   The API key must have the webhook option enabled. Post-call analysis data is only posted back to Slack when the key is designated as a webhook key.

4. Save the API key

   Paste the webhook key into Retell API Key and select Save API key. Confirm that the status shows Saved before continuing.

   Retell AI supports only one active webhook integration at a time. If you are also using Notion or Zoho, choose which integration receives webhook events.

   
5. Choose the outbound caller ID

   Select the Retell phone number used for outbound calls. If an agent option appears, choose the default agent or keep the Retell account default.

   
6. Set the default notification channel

   Choose the Slack channel that receives results when a call does not specify one. For a private channel, first run /invite @Retell AI in that channel.

   

Register the Retell webhook

1. Copy the generated webhook URL

   In the setup wizard, find Register the Webhook URL in Retell and select Copy webhook URL.

   
2. Add the webhook URL to the Retell agent

   Open the Retell dashboard, select Agents, and open the agent used for Slack. Expand Webhook Settings, paste the URL into Agent Level Webhook URL, and select Test. Under Webhook Events, make sure call_analyzed is enabled so Retell can send the post-call result. Save or publish the changes.

   

Place an outbound call from Slack

Use the slash command for the fastest end-to-end test.

1. Run the slash command

   In a channel where Retell AI can post, enter the command below with a valid E.164 destination number. Slack displays a private confirmation when the call starts.

   /retell-call [phone]
   

   
2. Review the post-call message

   After Retell analyzes the call, review the Slack message for the summary, duration, direction, sentiment, transcript details, and recording link.

   

Troubleshooting

Problem	Resolution
Slack is not connected	Select Connect Slack in App Home, approve access, then reopen the Home tab.
Setup will not complete	Confirm the API key, caller ID, default channel, and webhook test are complete.
Webhook test fails	Copy the full URL without editing it and complete the Slack connection before testing.
Slash command says not connected	Finish the setup wizard. An admin may need to reconnect or reinstall the app.
Invalid phone number	Use E.164 format with a leading plus and country code, without brackets or spaces.
No post-call message	Check the originating channel, invite Retell AI to private channels, and enable call_analyzed.
Message goes to the wrong channel	Update the default notification channel in the setup wizard.
Channel is not accessible	Invite Retell AI to the private channel or use an accessible public or default channel.
Wrong agent or caller ID	Update the default agent and caller ID in the wizard and confirm they match Retell.