google-cal-mcp

MCP server for Google Calendar - list, create, update, and manage calendar events.

Use Cases

Schedule meetings: "Set up a 30-min sync with Sarah next week" → finds a free slot, creates the event with a Meet link, and sends the invite.

RSVP to invites: "Accept the team offsite but decline the vendor demo" → responds to pending invitations automatically.

Find availability: "When am I free this Thursday afternoon?" → queries your calendar and returns open slots.

Reschedule events: "Move my 1:1 with Alex to Friday at 2pm" → updates the event and notifies attendees.

Daily briefing: "What's on my calendar today?" → lists all events with times, locations, and attendees.

Block focus time: "Block 2 hours tomorrow morning for deep work" → creates a calendar event to protect your time.

(These are just examples - any workflow that needs calendar access can use this.)

Setup

1. Create Google OAuth credentials

1. Go to Google Cloud Console
2. Create a new project (or use existing)
3. Enable the Google Calendar API
4. Go to APIs & Services → OAuth consent screen, set up consent screen
5. Go to APIs & Services → Credentials → Create Credentials → OAuth client ID
6. Choose Web application
7. Add http://localhost:3000/callback to Authorized redirect URIs
8. Note your Client ID and Client Secret

2. Run the server

GOOGLE_CLIENT_ID='your-client-id' \
GOOGLE_CLIENT_SECRET='your-client-secret' \
MCP_TRANSPORT=http \
npm start

The server runs on http://localhost:3000 by default. Change with PORT=3001.

3. Add to your MCP client

claude mcp add --transport http google-cal-mcp http://localhost:3000/mcp

Architecture

This server acts as an OAuth proxy to Google:

graph LR
    A[MCP client] <--> B[google-cal-mcp] <--> C[Google OAuth/API]

1. Server advertises itself as an OAuth authorization server via /.well-known/oauth-authorization-server
2. /register returns the Google OAuth client credentials
3. /authorize redirects to Google, encoding the client's callback URL in state
4. /callback receives the code from Google and forwards to the client's callback
5. /token proxies token requests to Google, injecting client credentials
6. /mcp handles MCP requests, using the bearer token to call Calendar API

The server holds no tokens or state - it just proxies OAuth to Google.

Tools

Tool	Description
Calendars
calendars_list	List all calendars the user has access to
calendarlist_insert	Subscribe to a shared calendar
calendarlist_update	Update calendar settings (color, visibility, reminders)
calendarlist_delete	Unsubscribe from a calendar
Events
events_list	List events in a time range with search/filter
event_get	Get details of a specific event
event_create	Create a new event with attendees and Meet link
event_update	Update an existing event
event_delete	Delete an event
event_respond	RSVP to an invitation (accept/decline/tentative)
event_move	Move event to a different calendar
event_instances	Get instances of a recurring event
Availability
freebusy_query	Find free/busy times for scheduling
Sharing
acl_list	List who has access to a calendar
Colors
colors_get	Get available color palette for calendars/events

Calendar API Scopes

• calendar - Full access to calendars
• calendar.events - Read/write events

Contributing

Pull requests are welcomed on GitHub! To get started:

1. Install Git and Node.js
2. Clone the repository
3. Install dependencies with npm install
4. Run npm run test to run tests
5. Build with npm run build

Releases

Versions follow the semantic versioning spec.

To release:

1. Use npm version <major | minor | patch> to bump the version
2. Run git push --follow-tags to push with tags
3. Wait for GitHub Actions to publish to the NPM registry.