Descriptions:
Bart Slodyczka walks through building a production-ready AI voice agent for inbound business calls, integrating Retell AI as the phone-facing voice layer with n8n handling backend automation. The demo uses a fictional automotive shop scenario where the AI agent — Sophie — answers FAQ questions sourced from an uploaded PDF, checks Google Calendar availability, and books service appointments, all within a single phone call. The live call demo at the start makes the capability immediately concrete.
The Retell AI configuration section covers selecting an AI brain model (GPT-4.1 as the starting point), choosing voices from ElevenLabs or OpenAI, understanding the latency metric (1,300ms baseline), and using the built-in end-call function to prevent runaway sessions. Bart then connects Retell AI to n8n via a custom function, turning n8n into the automation engine that processes booking requests and interacts with external services.
A particularly instructive segment addresses a real integration problem: Retell AI and Google Calendar expect incompatible date and time formats. Bart demonstrates writing a prompt for ChatGPT to generate an n8n code node that transforms the incoming time and date variables into the ISO format Google Calendar requires, including dynamic service duration logic. The workflow also includes an if-node to handle unavailable slots by suggesting an alternative time — a practical pattern applicable well beyond automotive bookings.
📺 Source: Bart Slodyczka · Published January 05, 2026
🏷️ Format: Hands On Build
