Book calendar appointments with availability checks in Google Calendar

Quick overview This workflow is triggered by another n8n workflow to verify a requested appointment slot and, if available, books a 30‑minute event in Google Calendar, returning a booked/unbooked response with formatted date/time details. Full setup guide: https://uzzaman.dev/guides/n8n-google-calendar-availability-booking/ How it works 1. Receives appointment details (name, phone, service type, preferred date, preferred time) when called by another n8n workflow. 2. Calls a separate “Check Slot Availability” workflow to determine whether the requested slot is available. 3. If the slot is available, builds ISO start/end timestamps for a 30-minute appointment window. 4. Creates the appointment as a Google Calendar event with a summary and description populated from the input details. 5. Returns a success payload with booked: true and formatted preferred date/time, or returns booked: false with an error code when the slot or calendar booking fails. Setup 1. Create or identify a “Check Slot Availability” workflow and update the referenced workflow ID/name so it returns an available boolean. 2. Add a Google Calendar OAuth2 credential and set the target calendar (email/ID) in the Google Calendar event creation step. 3. Ensure the calling workflow passes name, servicetype, preferreddate (ISO date), preferredtime (HH:mm), and phone, and adjust the default 30-minute duration if needed. Requirements - External AI voice platform (Vapi, Retell, or similar) & Published appointment management sub-workflows - MCP tools for Vapi and Retell voice agents - A configured "Check Slot Availability" sub-workflow (or your own equivalent) - Calling workflow must pass name, servicetype, preferreddate, preferredtime, phone Customization - Change the default 30-minute appointment duration in the event-creation step - Swap the Google Calendar node for a different calendar/CRM system - Adjust the fields included in the event summary/description