When Google Revokes Your Calendar Agent Connection

If an agent could read your calendar yesterday but cannot today, first separate a revoked Google OAuth connection from a network failure or a missing calendar grant. Repeatedly retrying a write does not restore permission.

What CalendarMCP checks

The signed-in dashboard probes each saved connection by asking Google for one calendar list entry. The health endpoint classifies a missing refresh token, server misconfiguration, a recognizable revocation response, or another unreachable result. It labels an invalid_grant response oauth_revoked and offers reconnect; an ordinary failed probe is not automatically treated as revoked. A probe on one connection does not verify every calendar or every API-key permission.

Google's OAuth web-server guide explains refresh-token use and invalidation. Do not publish a universal token lifetime: revocation, user action, and consent configuration can change the outcome.

Recover without guessing

1. Open the dashboard while signed in and identify the failing account, not merely the key that reported an error.
2. If the account says Revoked, use its reconnect action and complete Google consent for that same account. Do not paste a refresh token into an agent prompt.
3. Run the dashboard connection test, then use list_calendars with the affected API key to check the intended calendar's enabled state and read/write grants.
4. If the status is Needs attention rather than Revoked, investigate the reported cause or a temporary Google failure before changing credentials.

The live homepage offers Connect Google Calendar for a new connection. Existing users should use their account's reconnect control so they do not confuse a second account connection with repairing the first. The homepage click records connect_started; it is not evidence that consent finished or that an agent has working permissions.