← Back to Blog
·3 min read

Build a Free AI Voice Receptionist: Never Miss a Client Call Again

Learn how to create a fully automated AI voice agent that answers calls 24/7 and books appointments directly into Google Calendar—using completely free tools.

By Tnia Team
AI phone callVoice AgentsBooking Agent

In 2026, small businesses and service providers are still losing potential clients simply because they can't answer every incoming call. What if you could have a professional, human-like receptionist working 24/7—without paying a salary or any tool subscriptions?

The good news: It's possible today using completely free tiers of powerful platforms. In this guide, we'll walk through how to build a fully automated AI voice agent that answers calls, understands natural speech, confirms details, and books appointments directly into Google Calendar.

This setup is perfect for dental clinics, consultants, coaches, or any appointment-based business tired of playing phone tag.

Why You Need an AI Voice Receptionist Now

Missed calls mean missed revenue. Clients expect immediate responses, and voicemail often leads to lost leads. An AI receptionist:

  • Answers calls instantly, day or night
  • Handles natural conversations (e.g., "I'd like to book on January 3rd at 11 AM")
  • Confirms details to avoid errors
  • Automatically creates calendar events
  • Costs $0 using free plans

No more manual scheduling or no-shows eating into your profits.

The Tools You'll Use (All Free to Start)

  • Vapi.ai: The leading platform for building advanced voice AI agents. It handles realistic speech, intent recognition, and phone integration.
  • Make.com: A no-code automation tool (formerly Integromat) that connects everything via webhooks.
  • Google Calendar: For seamless appointment booking.

Step-by-Step Guide to Building Your AI Receptionist

1. Set Up Your Voice Agent in Vapi

  • Sign up for a free account at vapi.ai.
  • Create a new assistant (e.g., name it "Alex, Scheduling Assistant").
  • Define the prompt: Make it friendly and focused on booking appointments.
  • Add tools: Create a custom tool for booking that sends data via POST to a webhook.

2. Create the Automation in Make.com

  • Sign up for the free plan at make.com.
  • Build a new scenario starting with a Webhook module.
  • Copy the webhook URL and paste it into your Vapi tool configuration.
  • Add a Google Calendar module to create events based on the incoming data (date, time, client name).
Pro Tip: Always pass the full date (including year) in parameters to avoid mix-ups with relative dates like "January 3rd."

3. Test and Deploy

  • Simulate calls in Vapi's dashboard.
  • Watch as the agent confirms the appointment and adds it to your calendar.

The result? A caller says their preferred slot, the AI confirms, and the event appears instantly—no human intervention needed.

Common Pitfalls and Fixes

  • Ensure webhook responses are proper JSON.
  • Test thoroughly for date parsing issues.
  • Start simple, then add features like availability checks.

This DIY approach is powerful for basic setups, but for custom branding, advanced integrations, or scaling across multiple lines, professional help ensures it's flawless.

At Tnia, we specialize in building tailored voice AI agents for businesses just like yours—handling complex flows, multi-language support, and seamless CRM integrations.

Ready to automate your front desk and capture every lead? Get in touch to discuss your requirements.