Overview

This workflow allows you to trigger custom logic in n8n directly from Retell’s Voice Agent using Custom Functions. 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 who want to extend Voice Agent functionality with real-time custom workflows or AI-generated responses.

Prerequisites

– Have a Retell AI Account
– A Retell agent with a Custom Function node in its conversation flow
– Set your n8n webhook URL in the Custom Function configuration
– (Optional) Familiarity with Retell’s Custom Function docs

Start a conversation with the agent (text or voice)Retell Agent Example

To get you started, we’ve prepared a Retell Agent ready to be imported, that includes the call to this template. Import the agent to your Retell workspace. 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
3. Edit the function
4. Modify the URL
5. Modify the logic in the Set node or replace it with your own custom flow
6. 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 if you’re interested in analyzing your Retell Agent conversations.