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. - 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.
At a glance
Connect Retell Voice Agents to custom functions is a ready-made n8n workflow you import as a workflow JSON file — no build required. It connects Slack. It's free to download. Follow the 5-step import below to go live in minutes.
- Platform
- n8n
- Connects
- Slack
- Modules
- 3
- Price
- Free
- Version
- v1.0

About this workflow
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 (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 - 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 (top-right button on your agent's page) - 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. 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 if you're interested in analyzing your Retell Agent conversations.
How to import this n8n workflow
- 1
Download the workflow JSON file after purchase.
- 2
Open n8n → click the menu → Import from File.
- 3
Select the downloaded JSON and import.
- 4
Set up credentials for each node that requires them.
- 5
Click Execute Workflow to test, then activate.
Setup guide
Setup guide included
Purchase to unlock the full step-by-step guide
Related N8n workflows
Get Slack messages for new Planyo reservations
Create Google Calendar events from new Slack messages
Share city-specific Google Analytics reports to Google Sheets and Slack
Detect financial risk and orchestrate compliance with GPT‑4o, Slack and email
Create new Slack Status from given topics using OpenAI
Google trend data extract & summarization with Bright Data & Google Gemini
Create a branded AI-powered website chatbot
Personalized AI tech newsletter using RSS, OpenAI and Gmail
Reviews
No reviews yet
Be the first to buy and share your experience.
Leave a review
Sign in to share your experience with this workflow.
Create a free account to purchase workflows.
- JSON blueprint — instant download
- Setup guide PDF included
- 5 downloads · valid 30 days
- Works with n8n
Need help setting this up?
Book a 3-hour live setup session with an Agility consultant.
- Configure live on Google Meet / Zoom
- Free follow-up if workflow has defects
- Platform expert assigned to you