Vapi Voice Agent + Google Calendar Appointment Webhooks (n8n)

Automatically route Vapi voice calls to Google Calendar bookings—through secure webhooks in n8n

This n8n workflow powers a Vapi Voice Agent with two webhook endpoints that check availability and book appointments in Google Calendar. It validates requests using a shared secret, enforces opening days/hours and minimum notice, and returns structured tool results Vapi can use during the call.

What this workflow does

• Exposes two webhook endpoints for Vapi tool calls: check_availability and book_appointment.
• Validates security by checking a shared webhookSecret from the request headers and parsing the incoming tool payload into a normalized request format.
• Checks availability by querying Google Calendar free/busy across a configurable search window and returning whether the slot is available (plus nearest alternatives).
• Validates booking requests by verifying required customer details and ensuring the requested time fits configured opening days/hours and minimum notice rules.
• Re-checks free/busy for the exact requested slot immediately before booking to prevent race conditions.
• Creates a Google Calendar event with your configured title and includes the caller’s details in the event description.
• Responds to Vapi with a structured tool-result response (e.g., status: ok) or a clear error code.

Use cases

• Let callers book meetings via voice and have confirmations reflected instantly in Google Calendar.
• Offer “next available times” during a call when requested slots are unavailable.
• Ensure bookings respect your operational schedule (opening hours + notice period) without manual coordination.

Technical details

• Google Calendar integration: OAuth2 credential used for free/busy lookup and event creation.
• n8n nodes used: webhook, if, set, code, switch, and sticky note.
• Setup highlights: configure webhookSecret, confirm the secretHeader name, set calendarId and timezone, then define opening days/hours and appointment length.