Gmail MCP Server
This server is a remote Model Context Protocol (MCP) server for Gmail. A model can use it to read, search, label and draft email, and to send drafts. The server runs on Cloudflare Workers and on Bun. It uses the MCP server template 2.1 and the official MCP TypeScript SDK 2.3.0.
The server URL is the deployed Worker's MCP_PUBLIC_URL, for example https://gmail-mcp.<subdomain>.workers.dev/mcp.
The server uses protocol version 2026-07-28. It also accepts clients that use the 2025 protocol versions.
[!WARNING] You connect this server to your MCP client at your own risk. A model can make mistakes. Examine what the tools do, and examine changes in Gmail. The server can send email that is in a draft.
Tools
The server writes to Gmail only through drafts and labels. It sends email only with send_draft.
Connect a client
Use the server URL and the Streamable HTTP transport. The client signs you in with Google the first time.
Alice and Wonderlands use the same URL.
Authentication
The server is its own OAuth authorization server, in front of Google's OAuth. MCP clients do not receive Google tokens.
- The client registers at
/registerand signs the user in at/authorize. The client must use PKCE S256. - The server sends the user to Google. Google asks for the three Gmail scopes.
- Google returns the user to the server's
/oauth/callback. The server keeps the Google tokens, encrypted. - The client gets a code, and exchanges the code at
/tokenfor an access token and a refresh token. These tokens are opaque and have meaning only for this server. - On each MCP request, the server finds the Google token for the access token. If the Google token expires in less than one minute, the server refreshes it first. The tools use the Google token. They do not see the client's token.
For the complete flow, the storage and the redirect rules, refer to docs/oauth.md.
Configuration
The deployment settings are in wrangler.production.jsonc (Workers; gitignored, with wrangler.production.example.jsonc as its shape) or .env (Bun). .env.example describes all variables.
Secrets:
The Google endpoints, the Gmail scopes and the offline-access parameters are constants in src/services/google-oauth.ts. For the setup at Google and at Cloudflare, refer to docs/deploy.md.
Development
Requirements: Bun 1.4 or later, and Node.js 22.18 or later.
-
Install the dependencies:
bun install -
Copy
.env.exampleto.env. SetPROVIDER_CLIENT_ID,PROVIDER_CLIENT_SECRETandRS_TOKENS_ENC_KEY. At Google, allow the redirect URIhttp://127.0.0.1:3000/oauth/callback. -
Start the server:
bun run devThe server URL is
http://127.0.0.1:3000/mcp. To use the Cloudflare local runtime, runbun run dev:worker(port 8787). Put its secrets in.dev.vars. -
Before you commit, run the checks:
bun run check bun run test:smoke
bun run check does the type check, the lint check and the tests. bun run test:smoke starts the real server on Bun and on workerd. It signs in through a Google stand-in on loopback and calls the tools. No test uses the network.
Project structure
src/
server.ts Identity, Runtime, Deps, and the hooks that connect the OAuth proxy
settings.ts The Google client, the encryption key, the redirect allowlist
tools/ One file for each tool; shared/ has schemas and helpers
services/ The Gmail API client, and google-oauth.ts: Google as the OAuth provider
oauth/ The OAuth proxy. It is the same for every provider (docs/oauth.md)
platform/ Template code. Do not change it
bun.ts Entry point for Bun: file storage
worker.ts Entry point for Workers: KV and the NativeOAuthAuthority Durable Object
tests/ Tests for the tools, the proxy and the platform; fixtures from before 1.1.0
scripts/ Smoke tests and the Google stand-in
For the template's concepts (the request path, defineTool, the error policy, the configuration checks), refer to the template documentation.