google-workspace-mcp

An MCP server that gives Claude Code write access to a personal Google account — Gmail, Drive, Calendar, Sheets, and YouTube — backed by a self-owned Google Cloud OAuth client rather than a hosted third-party connector. It can send real email, not just draft it.

23 tools across 5 Google APIs. Runs locally over stdio.

You:    email me a summary of today's calendar
Claude: [calendar_list_events] → 4 events
        [gmail_send_email]     → delivered

Why own the OAuth client

The hosted Google connectors are read-mostly. Making Claude Code act — send a real email, create a real invite, write a real spreadsheet cell — means holding the OAuth client yourself. That single decision drives most of what's interesting below.

Related MCP server: gsheets-mcp

Design notes

Least-privilege scopes, chosen to avoid a paid security review

Google classifies gmail.readonly and drive.readonly as Restricted scopes. Shipping an app that uses them requires a CASA security assessment — a paid, recurring third-party audit. That is not a sensible cost for a single-user personal tool, so this server requests only write scopes:

Reading arbitrary Gmail and Drive content is left to the existing claude.ai connectors. The two halves compose: read there, act here.

The refresh token expires every ~7 days — this is expected

The OAuth client sits in Google's Testing publishing mode, and Google invalidates refresh tokens for testing-mode apps after 7 days of inactivity. Auth breaking after a week away is normal maintenance, not a bug:

npm run check-auth   # is the stored token still good?
npm run authorize    # re-consent in the browser; rewrites credentials/token.json

Moving to "In production" would remove the expiry but triggers exactly the verification review the scope choices above were made to avoid. For a single-user setup, periodic re-authorization is the cheaper trade.

Irreversible tools say so in their own descriptions

A tool description is the only thing the model reads before deciding to call it, so the warnings live there rather than in a confirmation layer the model can route around. From src/gmail.js:

Sends an email immediately from the authorized Gmail account, optionally with file attachments. This is a real send with no draft/review step and cannot be undone.

calendar_create_event and sheets_write_range carry equivalent warnings.

Several tools are externally visible under your real identity: gmail_send_email delivers to real inboxes, calendar_create_event with attendees emails invitations, and the YouTube comment tools post publicly. They are ordinary tools — but they're the ones where a mistake is visible to other people.

Refreshed tokens are persisted

googleapis emits a tokens event when it silently refreshes an access token. src/auth.js listens and merges the result back to disk, so a long-lived session doesn't lose its refresh token across restarts.

Setup

Requires Node 20+.

1. Create the OAuth client

1. In the Google Cloud Console, create a project.

2. Enable the Gmail, Google Calendar, Google Drive, Google Sheets, and YouTube Data v3 APIs.

3. Under APIs & Services → OAuth consent screen: External, publishing status Testing, and add your own Google account under Test users.

4. Under Credentials, create an OAuth client ID of type Desktop app.

5. Download the JSON to credentials/client_secret.json.

credentials/ is git-ignored. See credentials/client_secret.example.json for the expected shape.

2. Authorize

npm install
npm run authorize

Opens a loopback listener on localhost:53682, prints a consent URL, and writes the refresh token to credentials/token.json. Google shows an "unverified app" warning — expected for a Testing-status client only you can use.

3. Register with Claude Code

claude mcp add google-workspace --scope user -- node /absolute/path/to/google-workspace-mcp/src/index.js

Then claude mcp list to confirm it connected.

Tools

Gmail

Calendar

Drive / Sheets

YouTube

Layout

src/auth.js            OAuth client construction, token load/refresh persistence
src/gmail.js           MIME assembly (incl. base64 attachments) + gmail_* tools
src/calendar.js        calendar_* tools
src/drive.js           drive_* tools
src/sheets.js          sheets_* tools
src/youtube.js         youtube_* tools
src/index.js           McpServer construction + stdio transport
scripts/authorize.js   one-time / periodic OAuth consent flow
scripts/check-token.js token health check
scripts/smoke-test.js  end-to-end check across the API surfaces
test/tools.test.js     schema + MIME tests — no network, no credentials

Tests

npm test

Exercises the tool registry and the MIME builder only: no network, no credentials, safe in CI. Asserts that all 23 tools register under unique names, that registration never eagerly reaches for a token, that the tools capable of irreversible external side effects declare that in their descriptions, and that Gmail MIME assembly produces well-formed multipart messages with RFC 2045 line wrapping and base64url encoding.

Auth files

Both live in credentials/, which is git-ignored:

• client_secret.json — the OAuth client, downloaded from Google Cloud Console

• token.json — access + refresh tokens, written by npm run authorize

Neither has ever been committed. If credentials/ is lost, re-download the client secret and re-run npm run authorize.

Notes

• Depends on googleapis, which is heavy (~109 MB of the ~126 MB node_modules). That is the package, not a mistake.

• Scopes are requested up front at authorize time. Adding a new API later means re-running npm run authorize so the new scope is granted.

• package.json pins an override of gaxios to ^7.3.0. googleapis-common still resolves an older gaxios, which drags in rimraf → glob → minimatch → brace-expansion and a high-severity DoS advisory. The override is what takes npm audit to zero; removing it silently reintroduces six high-severity findings and ~37 packages. Drop it once googleapis-common ships a newer gaxios itself.

Privacy policy

Google requires a published policy on the consent screen even for a Testing-status app: brettadams0.github.io/google-workspace-mcp-policy (source).

License

MIT — see LICENSE.