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Allow AI systems to list, create, update, and manage Google Calendar events.
About
Allow AI systems to list, create, update, and manage Google Calendar events.
Security Report
4.2
Use Caution4.2High RiskThis Google Calendar MCP server implements OAuth delegation with reasonable security practices, but has several concerns that warrant attention. The server properly requires authentication for most operations, implements token validation, and avoids hardcoding secrets. However, the token validation mechanism has a critical flaw (caching based on opaque tokens without verification), the /authorize endpoint lacks CSRF protection, and there are input validation gaps in multiple tools. These issues are mitigated by the fact that tokens originate from Google's OAuth flow and the server operates as a proxy, but the implementation should be hardened. Supply chain analysis found 5 known vulnerabilities in dependencies (1 critical, 2 high severity). Package verification found 1 issue (1 critical, 0 high severity).
7 files analyzed · 16 issues found
Security scores are indicators to help you make informed decisions, not guarantees. Always review permissions before connecting any MCP server.
Permissions Required
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Unverified package source
We couldn't verify that the installable package matches the reviewed source code. Proceed with caution.
What You'll Need
Set these up before or after installing:
Google OAuth access token with Calendar scopes.Required
Environment variable: GOOGLE_ACCESS_TOKEN
Transport type.
Environment variable: MCP_TRANSPORT
Google OAuth client ID.
Environment variable: GOOGLE_CLIENT_ID
Google OAuth client secret.Required
Environment variable: GOOGLE_CLIENT_SECRET
How to Install
Add this to your MCP configuration file:
{
"mcpServers": {
"io-github-domdomegg-google-cal-mcp": {
"env": {
"MCP_TRANSPORT": "your-mcp-transport-here",
"GOOGLE_CLIENT_ID": "your-google-client-id-here",
"GOOGLE_ACCESS_TOKEN": "your-google-access-token-here",
"GOOGLE_CLIENT_SECRET": "your-google-client-secret-here"
},
"args": [
"-y",
"google-cal-mcp"
],
"command": "npx"
}
}
}Documentation
View on GitHubFrom the project's GitHub README.
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
- Go to Google Cloud Console
- Create a new project (or use existing)
- Enable the Google Calendar API
- Go to APIs & Services → OAuth consent screen, set up consent screen
- Go to APIs & Services → Credentials → Create Credentials → OAuth client ID
- Choose Web application
- Add
http://localhost:3000/callbackto Authorized redirect URIs - 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]
- Server advertises itself as an OAuth authorization server via
/.well-known/oauth-authorization-server /registerreturns the Google OAuth client credentials/authorizeredirects to Google, encoding the client's callback URL in state/callbackreceives the code from Google and forwards to the client's callback/tokenproxies token requests to Google, injecting client credentials/mcphandles 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 calendarscalendar.events- Read/write events
Contributing
Pull requests are welcomed on GitHub! To get started:
- Install Git and Node.js
- Clone the repository
- Install dependencies with
npm install - Run
npm run testto run tests - Build with
npm run build
Releases
Versions follow the semantic versioning spec.
To release:
- Use
npm version <major | minor | patch>to bump the version - Run
git push --follow-tagsto push with tags - Wait for GitHub Actions to publish to the NPM registry.
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