Vapi AI + Google Calendar API + Make.com Automation for life Insurance Appointment Booking

Title: Vapi AI + Google Calendar API + Make.com Automation for Appointment Booking Description: I am Hugo Rojas, a MetLife insurance advisor in Mexico. I need help finishing an automation system for my personal insurance advisory business. The system uses Vapi AI to call existing clients in Spanish and schedule appointments for a dividend withdrawal process. I need a reliable workflow that checks my real Google Calendar availability, prevents double-booking, creates the event, updates Google Sheets, and later supports WhatsApp confirmations through Make.com. Current setup: * Vapi assistant is already created. * OpenAI API is connected. * Google Calendar is connected. * Google Sheet is already created. * WhatsApp Business Cloud is connected to Make.com. * WhatsApp templates are already approved by Meta. * Vapi’s native calendar tools caused timezone and double-booking issues, so I need a more reliable solution. Main task: Build a reliable booking tool using either Make.com or a small custom API. The tool must: 1. Receive appointment data from Vapi: * customer name * policy number * date * time * product * phone number if available 2. Handle Chihuahua, Mexico timezone correctly. 3. Check Google Calendar for 30-minute availability. 4. Prevent overlapping appointments. 5. Create the event only if the time slot is free. 6. If the requested time is busy, return a busy response and ideally suggest 2 available alternatives. 7. Send a structured response back to Vapi. 8. Update Google Sheets with the appointment result. 9. Prepare the WhatsApp confirmation flow in Make.com. Event title format: Customer Name - Policy [Policy Number] Example: Carlos Pérez - Policy 123456789 Important: The booking logic must not depend only on the AI prompt. The calendar conflict check must be enforced technically by Make.com or a custom API. The AI assistant will speak with clients in Mexican Spanish, but the technical setup and documentation can be in English. Deliverables: * Working Vapi custom tool. * Working Make.com scenario or custom API. * Google Calendar conflict checking. * Calendar event creation without double-booking. * Structured response back to Vapi. * Google Sheets update. * Basic WhatsApp confirmation structure. * Short documentation or Loom video. Please start your proposal with the word “CHIHUAHUA” so I know you read the full post. Questions: 1. Have you built Vapi custom tools before? 2. Have you worked with Google Calendar FreeBusy or conflict checking? 3. Would you build this with Make.com only or with a small API? Why? 4. How would you prevent double-booking? 5. How long would it take to deliver a working version?