google-chat-mcp

Google Chat as MCP tools. Read, search and write to your spaces, direct messages and sidebar from Claude Code, Claude Desktop, or any other MCP client.

A single Go binary that speaks MCP over stdio. It runs as a subprocess of your client, on your own machine, against your own Google account. There is no server to host, no shared deployment and no service account: you create a Google OAuth client, log in once, and the refresh token stays in your OS keyring.

Install

go install github.com/mmedum/google-chat-mcp/v2/cmd/google-chat-mcp@latest

Or take a signed archive from the latest release — Linux, macOS and Windows, on amd64 and arm64 — and verify it before you run it:

sha256sum -c checksums.txt --ignore-missing

# The checksum file is signed with a keyless Sigstore certificate tied to
# the release workflow's identity. The bundle carries both.
cosign verify-blob checksums.txt \
  --bundle checksums.txt.bundle \
  --certificate-identity-regexp 'https://github\.com/mmedum/google-chat-mcp/' \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com

# And the archive itself carries build provenance.
gh attestation verify google-chat-mcp_*.tar.gz --repo mmedum/google-chat-mcp

Every archive also ships an SBOM, so you can see what is inside a binary you did not build.

Claude Desktop

Every release also carries a .mcpb bundle. Open it and Claude Desktop installs the server and asks for your OAuth client JSON — no config file to edit. It covers macOS, Windows and Linux on both architectures each: macOS through a universal binary, Windows through amd64, and Linux through a small launcher that picks the right binary at start, because a bundle manifest has no key for the architecture. Its SHA-256 is in the same signed checksums.txt. The release is listed in the MCP registry as io.github.mmedum/google-chat-mcp.

The bundle does not log you in. Install the binary as well, run google-chat-mcp login once, and the bundle picks up the same credentials. Claude Code does not install .mcpb files, so it uses the command below.

Set up Google

You need your own OAuth client. It takes about fifteen minutes once, and docs/gcp-setup.md walks through it. In short: create a project, enable the Google Chat API and the People API, configure the consent screen with the scopes this server asks for, and create an OAuth 2.0 Client ID of type Desktop app. Download the JSON.

Then log in:

google-chat-mcp login --client-secret ./client_secret.json

Login opens your browser, or prints the URL when there is no browser to open (--no-browser forces that). The callback lands on 127.0.0.1 on a random port, with PKCE and state throughout. The refresh token goes into your OS keyring; if there is no keyring, it goes into a 0600 file and the command tells you so. On Windows a Go file mode only sets the read-only attribute, so what protects that file there is the ACL its directory inherits, not the mode.

google-chat-mcp status says which account is signed in and where the token lives. google-chat-mcp logout revokes the token at Google and deletes the local copy.

Logging in over SSH

The callback goes to the remote host's loopback address, and your browser is local, so forward the port. It is chosen at random and printed only once login is already waiting, so read it out of the printed URL — it appears percent-encoded, as 127.0.0.1%3A<port> — and in a second local terminal:

ssh -N -L <port>:127.0.0.1:<port> user@remote-host

Then open the URL locally. If ssh reports bind: Address already in use, cancel the login with Ctrl-C and run it again to draw another port.

Connect your client

Claude Code:

claude mcp add google-chat -- google-chat-mcp

Or, in a client config file:

{
  "mcpServers": {
    "google-chat": {
      "command": "google-chat-mcp"
    }
  }
}

Claude Desktop reads the same shape from its own config file. Use the binary's absolute path there if it is not on the app's PATH, or install the .mcpb bundle above and edit nothing.

Every setting is an environment variable, listed in docs/configuration.md. The three worth knowing now: GCM_READ_ONLY=true leaves out every tool that changes anything in Chat, GCM_PROFILE lets one machine hold a work account and a personal one, and GCM_LOCAL_DIR names the one directory files may be written to and read from. Without that last one the server touches no files at all, and the three tools that move them say so.

If something does not work, run google-chat-mcp doctor. It checks the credentials, the granted scopes and what Google actually answers, and names what is missing.

Tools