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Google Calendar: Update an event — MCP tool

Google Calendar MCP tool: Partially updates an event — reschedule, retitle, change guests, reminders or a single recurring occurrence.

Technical name: update_event

What task it solves

I want to change an existing event.

Applies a partial update (PATCH): only the provided fields change. Returns the updated event.

When to use it

Use it to reschedule (send BOTH the new start and end), rename, edit the description or guest list, add a Meet link, or change reminders. To touch one occurrence of a recurring series, pass that instance's id from list_event_instances; the master id changes every occurrence. Moving an event to a different calendar is move_event, not this.

What to provide

  • calendar_id, event_id — required.
  • Any of the create_event fields — optional, at least one: summary, description, location, times, attendees, recurrence, add_meet, reminders, transparency, visibility, color_id, guest permissions.
  • send_updates — optional. Guests hear about the change only with all.

What it returns

The updated event as compact JSON.

What changes in Google Calendar

The named fields of the live event are overwritten. A provided nested object replaces its predecessor wholesale: attendees replaces the ENTIRE guest list (fetch the event first and send the complete new list), reminders replaces all overrides.

Example request

Move tomorrow's design review to 15:00–16:00 and add pete@example.com to the guest list, notifying everyone.

Errors and limitations

A time change should carry both start_date_time and end_date_time (or both dates) — patching only one side can be rejected or produce a zero-length event. Not retried after an ambiguous failure — verify with get_event before re-sending. Needs writer/owner access (or guests_can_modify on the event).

Access also depends on token permissions, quotas, and upstream API limits.

Related MCP tools

Technical details