Google Calendar Workspace MCP Server

An MCP (Model Context Protocol) server for Google Calendar integration using service account authentication with domain-wide delegation. This server enables AI assistants to interact with Google Calendar to list events, create events, manage calendars, and query availability.

Features

List Events: View calendar events within a specified time range with filtering
Get Event Details: Retrieve complete information about specific events
Create Events: Create new calendar events with attendees, location, and descriptions
Update Events: Modify existing events (PATCH semantics - only provided fields are updated)
Delete Events: Remove events with optional notification to attendees
List Calendars: Discover available calendars
Query Free/Busy: Check availability and find busy time slots

Prerequisites

Google Cloud Project with Calendar API enabled
Service Account with domain-wide delegation
Google Workspace Admin access to grant calendar permissions

Setup

1. Create a Google Cloud Service Account

Go to Google Cloud Console
Create or select a project
Enable the Google Calendar API:
- Navigate to "APIs & Services" > "Library"
- Search for "Google Calendar API"
- Click "Enable"
Create a service account:
- Navigate to "IAM & Admin" > "Service Accounts"
- Click "Create Service Account"
- Provide a name and description
- Click "Create and Continue"
- Skip granting roles (not needed for domain-wide delegation)
- Click "Done"
Create a key for the service account:
- Click on the created service account
- Go to "Keys" tab
- Click "Add Key" > "Create new key"
- Select "JSON" format
- Download the key file
Note the service account's Client ID (found in the service account details)

2. Enable Domain-Wide Delegation

In the service account details, click "Show domain-wide delegation"
Check "Enable Google Workspace Domain-wide Delegation"
Save the changes
Note the Client ID (you'll need this for the next step)

3. Grant Calendar Permissions in Google Workspace Admin

Go to Google Workspace Admin Console
Navigate to "Security" > "Access and data control" > "API Controls"
Click "Manage Domain Wide Delegation"
Click "Add new"
Enter the service account's Client ID

In the "OAuth Scopes" field, add:

https://www.googleapis.com/auth/calendar

Click "Authorize"

4. Configure Environment Variables

Extract the following from your downloaded JSON key file:

client_email: The service account email
private_key: The private key (including -----BEGIN PRIVATE KEY----- and -----END PRIVATE KEY-----)

Set these environment variables:

export GCAL_SERVICE_ACCOUNT_CLIENT_EMAIL="your-service-account@your-project.iam.gserviceaccount.com"
export GCAL_SERVICE_ACCOUNT_PRIVATE_KEY="-----BEGIN PRIVATE KEY-----\nYour private key content\n-----END PRIVATE KEY-----"
export GCAL_IMPERSONATE_EMAIL="user@yourdomain.com"

Note: GCAL_IMPERSONATE_EMAIL should be the email address of the user whose calendar you want to access.

Installation

Using NPX (Recommended)

npx google-calendar-workspace-mcp-server

Using NPM

npm install -g google-calendar-workspace-mcp-server
google-calendar-workspace-mcp-server

Usage with Claude Desktop

Add this configuration to your Claude Desktop config file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "google-calendar": {
      "command": "npx",
      "args": ["google-calendar-workspace-mcp-server"],
      "env": {
        "GCAL_SERVICE_ACCOUNT_CLIENT_EMAIL": "your-service-account@your-project.iam.gserviceaccount.com",
        "GCAL_SERVICE_ACCOUNT_PRIVATE_KEY": "-----BEGIN PRIVATE KEY-----\nYour private key\n-----END PRIVATE KEY-----",
        "GCAL_IMPERSONATE_EMAIL": "user@yourdomain.com"
      }
    }
  }
}

Tool Groups

By default, all tools are enabled (read + write access). You can restrict the server to read-only operations by setting the ENABLED_TOOLGROUPS environment variable:

{
  "mcpServers": {
    "google-calendar": {
      "command": "npx",
      "args": ["google-calendar-workspace-mcp-server"],
      "env": {
        "GCAL_SERVICE_ACCOUNT_CLIENT_EMAIL": "...",
        "GCAL_SERVICE_ACCOUNT_PRIVATE_KEY": "...",
        "GCAL_IMPERSONATE_EMAIL": "...",
        "ENABLED_TOOLGROUPS": "readonly"
      }
    }
  }
}

Available tool groups:

Group	Tools Included
`readwrite`	All 7 tools (read + write) - included by default
`readonly`	Read-only tools: `list_calendar_events`, `get_calendar_event`, `list_calendars`, `query_calendar_freebusy`

When using only readonly, the write tools (create_calendar_event, update_calendar_event, delete_calendar_event) are not available.

Available Tools

list_calendar_events

Lists events from a calendar within an optional time range.

Parameters:

calendar_id (optional): Calendar ID (default: "primary")
time_min (optional): Start time in RFC3339 format
time_max (optional): End time in RFC3339 format
max_results (optional): Maximum events to return (default: 10, max: 250)
query (optional): Free text search query
single_events (optional): Expand recurring events (default: true)
order_by (optional): "startTime" or "updated"

Example:

List my events for the next week

get_calendar_event

Retrieves detailed information about a specific event.

Parameters:

event_id (required): The event ID
calendar_id (optional): Calendar ID (default: "primary")

Example:

Get details for event ID abc123

create_calendar_event

Creates a new calendar event.

Parameters:

summary (required): Event title
start_datetime OR start_date (required): Event start time
end_datetime OR end_date (required): Event end time
description (optional): Event description
location (optional): Event location
attendees (optional): Array of email addresses
calendar_id (optional): Calendar ID (default: "primary")

Example:

Create a meeting tomorrow at 2pm for 1 hour titled "Team Sync"

update_calendar_event

Updates an existing calendar event. Uses PATCH semantics - only the fields you provide will be updated; other fields remain unchanged.

Parameters:

event_id (required): The event ID to update
calendar_id (optional): Calendar ID (default: "primary")
summary (optional): New event title
description (optional): New event description
location (optional): New event location
start_datetime OR start_date (optional): New start time
end_datetime OR end_date (optional): New end time
attendees (optional): Updated array of attendee email addresses
send_updates (optional): "all", "externalOnly", or "none" - whether to send update notifications

Example:

Update event abc123 to change the title to "Team Standup"

delete_calendar_event

Deletes a calendar event.

Parameters:

event_id (required): The event ID to delete
calendar_id (optional): Calendar ID (default: "primary")
send_updates (optional): "all", "externalOnly", or "none" - whether to send cancellation notifications

Example:

Delete event abc123

list_calendars

Lists all calendars available to the authenticated user.

Parameters:

max_results (optional): Maximum calendars to return (default: 50, max: 250)

Example:

Show all my calendars

query_calendar_freebusy

Queries availability information for calendars.

Parameters:

time_min (required): Start time in RFC3339 format
time_max (required): End time in RFC3339 format
calendar_ids (required): Array of calendar IDs to check
timezone (optional): Time zone for the query

Example:

Check if I'm free tomorrow between 2pm and 4pm

Development

# Install dependencies
npm run install-all

# Build the project
npm run build

# Run in development mode
npm run dev

# Run tests
npm test

# Run integration tests
npm run test:integration

# Run all tests
npm run test:all

Security Considerations

Private Key Security: Never commit your service account private key to version control
Least Privilege: Only grant the minimum required OAuth scopes
Key Rotation: Regularly rotate service account keys
Access Logging: Monitor service account usage in Google Cloud Console

Troubleshooting

Authentication Failed

Verify service account credentials are correct
Ensure domain-wide delegation is enabled
Check that the correct OAuth scope is authorized in Admin Console
Verify the impersonate email address is correct

Permission Denied

Ensure the calendar scope (https://www.googleapis.com/auth/calendar) is granted in Google Workspace Admin Console
Verify the impersonated user has access to the calendar

Calendar Not Found

Check that the calendar ID is correct
Verify the impersonated user has access to the calendar
Use list_calendars to discover available calendar IDs

License

MIT

Contributing

See CONTRIBUTING.md for guidelines.