n8n Webhook Appointment Validator + Google Calendar Event

Instantly validate appointment requests and (optionally) create Google Calendar events

This n8n workflow receives booking requests via a webhook, checks whether the requested time is valid and available, and—when confirmed—creates a Google Calendar event before returning a clear JSON response to your system.

What this workflow does

• Receives a POST webhook request with appointment details (e.g., customer info, requested_start in ISO 8601, duration_min, business hours, and optional existing bookings).
• Validates required fields and verifies the requested slot falls within business hours.
• Checks for scheduling conflicts by ensuring the requested time does not overlap any provided existing bookings. It can also optionally ignore a matching booking when rescheduling.
• Returns one of three outcomes:
  • Invalid — includes field errors.
  • Conflict — returns up to three alternative available slots.
  • Confirmed — returns the chosen start/end times and a confirmation message.
• Creates a Google Calendar event when confirmed and dry_run is false, then marks the response with dispatched: true.
• Responds to the webhook caller with the final decision JSON.

Use cases

• Booking validation for a website form or chatbot that needs instant availability feedback.
• Scheduling reschedules by ignoring the existing booking being updated.
• SaaS operators integrating appointment booking with automatic calendar dispatch and structured webhook responses.

Technical details

• Google Calendar OAuth2 credential for event creation.
• Uses n8n nodes: webhook, if, code, http request, respond to webhook (plus supporting workflow notes).
• Designed for systems that POST the expected JSON fields to the webhook URL from the “Booking Webhook” node.