💬 Check appointment availability via authenticated webhook and Google Calendar
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Description
Quick overview
This workflow exposes an authenticated webhook that validates a proposed start/end time, checks Google Calendar availability for that interval, and returns a structured JSON response indicating whether the slot is available, busy, or could not be checked.
How it works
- Receives a POST webhook request authenticated via header auth with a JSON body containing start and end timestamps.
- Validates that start and end are RFC3339 timestamps with seconds and an explicit offset, start is in the future, and the interval is positive and no longer than 24 hours.
- If the request is valid, queries Google Calendar for free/busy availability for the provided time window.
- Formats the result as JSON with status (available or busy), a boolean available flag, and the normalized UTC start and end.
- Returns HTTP 200 for successful checks, HTTP 400 with validation errors for invalid requests, or HTTP 502 if Google Calendar cannot be queried without making an availability claim.
Setup
- Create a Header Auth credential for the webhook and configure your calling app to send the same header name and secret value.
- Add a Google Calendar OAuth credential and replace YOUR_CALENDAR_ID with the calendar ID you want to check.
- Keep the workflow inactive while configuring a unique webhook path and a dedicated test calendar. Send Content-Type: application/json and the configured authentication header, with start and end timestamps including seconds and a time-zone offset. Test a future free interval, a busy interval, invalid times and a provider permission failure. A provider failure must never return available. Activate only after those checks, then use the production webhook URL shown by n8n.
Requirements
- An n8n installation with Webhook, Code, IF, Respond to Webhook and Google Calendar nodes; a Google account and accessible calendar; Google Calendar OAuth credentials; and a calling application that can send an authenticated JSON POST request. No AI provider or model subscription is required.
Customization
- Change the webhook path and calendar. Add your own scheduling rules before the availability check for office hours, staff eligibility, lead time, buffers or holidays. Keep the separate invalid-request and provider-error branches.
Additional info
HTTP 200 returns status available or busy, a boolean available, and normalized UTC start and end. HTTP 400 returns invalid_request and validation errors. HTTP 502 returns unavailable without claiming that the interval is free. This is a snapshot for one interval. It neither generates a slot catalogue nor holds or creates an appointment. Calendar state can change after the check. Successful, error and manual execution saving are disabled in the export; review instance logging and retention before using real requests. Prepared by Benian Technologies: https://benian.ai/integrations/n8n-automation
🔗 Nodes Used
Webhook, Google Calendar
📥 Import
Download workflow.json and import into n8n:
Workflow menu → Import from File