Building AI Voice Agents with n8n and Retell AI: A Practical Guide

Source: Dev.to

The Architecture

Phone Call → Retell AI → Webhook → n8n → CRM/Database
                ↑                    ↓
                └──── Response ──────┘

Why This Stack?

• n8n – Open‑source, self‑hostable, powerful workflow automation.
• Retell AI – Realistic voice synthesis with an easy API integration.
• Flexibility – Connect to any CRM, database, or API.

Setting Up the Basics

1. Create a Retell AI Agent

Set up your voice agent in Retell AI with:

• Voice selection
• Base prompt / personality
• Webhook URL (your n8n endpoint)

2. Create n8n Webhook

Start your n8n workflow with a Webhook node that receives call data from Retell AI.

3. Process the Incoming Data

The webhook receives call data including:

• Caller phone number
• Transcript
• Intent detected
• Custom variables

4. Business Logic in n8n

Here’s where the magic happens:

• Lead Qualification – Score the lead based on responses.
• CRM Update – Push data to GoHighLevel, HubSpot, etc.
• Appointment Booking – Check calendar and book slots.
• Notifications – Alert your team via Slack, email, SMS.

5. Send Response Back

n8n can send dynamic responses back to Retell AI, such as:

• Next questions to ask
• Appointment confirmation details
• Custom information from your database

Real Example: Dental Appointment Booking

1. Patient calls.
2. AI greets and asks for name.
3. n8n checks if the caller is an existing patient in the CRM.
4. AI asks for preferred date/time.
5. n8n checks availability in the calendar.
6. AI confirms the appointment.
7. n8n creates the booking and sends a confirmation SMS.

Tips for Production

• Error Handling – Always have fallback responses.
• Logging – Log every interaction for debugging.
• Testing – Test edge cases before going live.
• Human Handoff – Provide an option to reach a human operator.

Conclusion

Building AI voice agents doesn’t have to be complicated. With the right tools and architecture, you can create systems that handle real business calls effectively.