Connect Retell Voice Agents to custom functions

Overview - This workflow allows you to trigger custom logic in n8n directly from Retell's Voice Agent using [Custom Functions](https://docs.retellai.com/build/conversation-flow/custom-functioncustom-function). - It captures a POST webhook from Retell every time a Voice Agent reaches a Custom Function node. - You can plug in any logic—call an external API, book a meeting, update a CRM, or even return a dynamic response back to the agent.

Who is it for For builders using [Retell](https://www.retellai.com/) who want to extend Voice Agent functionality with real-time custom workflows or AI-generated responses.

Prerequisites - Have a [Retell AI Account](https://www.retellai.com/) - A Retell agent with a Custom Function node in its conversation flow (see template below) - Set your n8n webhook URL in the Custom Function configuration (see "How to use it" below) - (Optional) Familiarity with [Retell's Custom Function docs](https://docs.retellai.com/build/conversation-flow/custom-functioncustom-function) - Start a conversation with the agent (text or voice)

Retell Agent Example To get you started, [we've prepared a Retell Agent](https://drive.google.com/file/d/1rAcsNz-f8SyuOxO0VJ84oPscYFpir4-/view?usp=sharing) ready to be imported, that includes the call to this template. - Import the agent to your Retell workspace (top-right button [on your agent's page](https://dashboard.retellai.com/agents)) - You will need to modify the function URL in order to call your own instance. - This template is a simple hotel agent that calls the custom function to confirm a booking, passing basic formatted data.

How it works - Retell sends a webhook to n8n whenever a Custom Function is triggered during a call (or test chat). - The webhook includes: - Full call context (transcript, call ID, etc.) - Parameters defined in the Retell function node - You can process this data and return a response string back to the Voice Agent in real-time.

How to use it 1. Copy the webhook URL (e.g. https://your-instance.app.n8n.cloud/webhook/hotel-retell-template) 2. Modify the Retell Custom Function webhook URL (see template description for screenshots) - Edit the function  - Modify the URL  3. Modify the logic in the Set node or replace it with your own custom flow 4. Deploy and test: Retell will hit your n8n workflow during the conversation

Extension Ideas - Call a third-party API to fetch data (e.g. hotel availability, CRM records) - Use an LLM node to generate dynamic responses - Trigger a parallel automation (Slack message, calendar invite, etc.)

👉 [Reach out to us](mailto:hello@agentstudio.io) if you're interested in analyzing your Retell Agent conversations.