google-mail-mcp

README

google-mail-mcp

Gmail as MCP tools. Read your mail without letting it read your assistant.

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 and no service account: you create a Google OAuth client, log in once, and the refresh token stays in your OS keyring.

It works inside a mailbox. A calendar invitation's event, a linked Drive file and a Chat space belong to servers built on those APIs.

Why google-mail-mcp

Every message was written by somebody other than you, and some of it is written to steer an AI assistant. So mail comes back inside blocks marked with a per-call boundary token; text a reader of the mail would not have seen — hidden styles, zero-width characters, text colored like its background — is removed and counted; nothing a message links to or embeds is fetched; and a link whose text names a different site from its target is flagged.

The writes that would make a persuaded assistant dangerous are not there. Forwarding, filters that forward and delegation are not implemented. Sending is not registered unless you turn it on, and then only a draft can be sent. Removal is trash; permanent deletion is not registered unless you turn it on, and is the only thing that asks Google for full mail access.

Reads are bounded. A thread comes back newest first within a character budget, with quoted replies and signatures collapsed to a line saying how much was hidden, and every omission says how to continue. Non-ASCII subjects, names and filenames decode in any charset.

Install

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

Or take an 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.
cosign verify-blob checksums.txt \
  --bundle checksums.txt.bundle \
  --certificate-identity-regexp 'https://github\.com/mmedum/google-mail-mcp/' \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com

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

Every archive ships an SBOM. Builds are reproducible: rebuilding a tag gives the same bytes.

Claude Desktop

Every release also carries a .mcpb bundle. Open it and Claude Desktop installs the server and asks for your OAuth client JSON. It covers macOS, Windows and Linux on both architectures. Its SHA-256 is in the same signed checksums.txt.

The bundle does not log you in. Install the binary as well, run google-mail-mcp login --client-secret <your client JSON> once, and the bundle uses the same credentials.

Set up Google

docs/gcp-setup.md has the whole of it: a Cloud project with the Gmail API enabled, a consent screen, the scopes for how you will run the server, and a Desktop app OAuth client. Then:

google-mail-mcp login --client-secret ~/path/to/client_secret.json
google-mail-mcp doctor

Every Gmail scope that reads mail is one Google calls restricted. For your own use that costs nothing, but an External client in Testing gets refresh tokens that expire after seven days; docs/runbook.md says what that looks like.

Logging in over SSH

The callback goes to the remote host's loopback address while your browser is local, so forward the port. Run google-mail-mcp login --no-browser: it prints the authorization URL and the exact ssh -L line for the port it picked. Run that line in a second local terminal, then open the URL locally.

Connect a client

Claude Code:

claude mcp add google-mail -- google-mail-mcp

Or, in a client config file:

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

Every setting is a GMAIL_* environment variable, listed in docs/configuration.md. The ones worth knowing now: GMAIL_READ_ONLY=true registers only the read tools and asks for read-only access; GMAIL_LOCAL_DIR is the one directory attachments may be saved to; GMAIL_PROFILE lets one machine hold several accounts.

Tools

Tool	What it does
get_profile	The signed-in account, its totals and the current history id
search_threads	Find conversations with a Gmail search
search_messages	Find single messages with a Gmail search
get_thread	Read a conversation, newest first, within a budget
get_message	Read one message, by id or by its Message-ID header
list_labels	Every label, optionally with counts
list_drafts	Unsent drafts
get_draft	Read one draft
list_changes	What changed since a history id, and when that cursor has expired
get_settings	Forwarding, vacation reply, send-as addresses, IMAP and POP, read-only
list_filters	The account's filters, with any that forward mail flagged
download_attachment	Save an attachment into GMAIL_LOCAL_DIR, never overwriting; only when that is set
create_draft	Save a new draft or a reply, threaded by the server; nothing is sent
update_draft	Change only the fields given, refusing a draft that changed since it was read
delete_draft	Delete a draft for good, with confirm: true
modify_labels	Add and remove labels on up to 100 messages or threads, reported per item
trash	Move up to 100 messages or threads to the trash, kept 30 days
restore	Take messages or threads out of the trash
create_label	Create a user label
update_label	Rename a user label or change how it shows
send_draft	Send a draft, naming every recipient who has not written in the thread; only with GMAIL_ENABLE_SEND=true
delete_permanently	Delete up to 100 messages or threads for good, with confirm: true; only with GMAIL_ENABLE_DESTRUCTIVE=true
delete_label	Delete a user label, with confirm: true; only with GMAIL_ENABLE_DESTRUCTIVE=true
update_signature	Set the signature of one of the account's addresses; only with GMAIL_ENABLE_SETTINGS=true
create_filter	Create a filter for mail that arrives from now on; it cannot forward; only with GMAIL_ENABLE_SETTINGS=true
delete_filter	Delete a filter, with confirm: true; only with GMAIL_ENABLE_SETTINGS=true
set_vacation	Turn the vacation reply on for contacts or the domain, or off; only with GMAIL_ENABLE_SETTINGS=true and GMAIL_ENABLE_SEND=true

Searches take Gmail's own search language in q, plus after and before as real instants — Gmail reads a date written inside q as midnight Pacific time. Every result states the quota it spent. Every write takes dry_run, names what it touches by id, and says what it changed, read from Gmail's answer. GMAIL_READ_ONLY=true leaves the writes out. The last seven tools are not registered at all unless their setting is on.

For clients that attach rather than call, gmail://threads/{id}, gmail://messages/{id} and gmail://labels carry the same text as get_thread, get_message and list_labels.

Safety

• Mail is data. It arrives marked, with what was hidden removed and counted, and no tool description tells a model to act on it.
• Nothing reaches another person by default. Drafts wait in Gmail to be sent, and by default no tool changes a setting. Forwarding is shown, never set.
• Settings are opt-in. With GMAIL_ENABLE_SETTINGS=true the server can set a signature and create or delete filters. A filter cannot forward, and one that trashes mail needs confirm: true. The vacation reply answers other people, so it also needs GMAIL_ENABLE_SEND=true, it only ever answers contacts or the account's domain, and turning it on needs confirm: true.
• Sending is opt-in and goes through a draft. With GMAIL_ENABLE_SEND=true, send_draft sends a draft exactly as it is stored. Every recipient not already in the thread must be written out in confirm_recipients, and a send Gmail does not confirm is never repeated.
• Removal is trash. Gmail keeps trashed mail for 30 days, and restore brings it back. By default the only permanent removal is delete_draft, which needs confirm: true. delete_permanently and delete_label exist only with GMAIL_ENABLE_DESTRUCTIVE=true, which also asks for the one scope that can delete; each call needs confirm: true.
• Files go to one directory. download_attachment writes only into GMAIL_LOCAL_DIR, under a name made safe, and never over an existing file.
• Logs never carry mail. No address, subject, body, label name or query; ids are cut to six characters. A test drives every tool with marker values and fails if one reaches a log, which is what makes a debug log safe to paste.
• Everything above is enforced in the server. Tool annotations are set, but they are hints a client may ignore.

docs/security.md has the whole of it.

Getting help

Run google-mail-mcp doctor first: it checks the client JSON, the token, the granted scopes and whether the Gmail API is enabled, and names what is missing. docs/runbook.md covers the common surprises. Then open an issue with doctor's output and the version. Do not paste a tool result: it is mail, and carries other people's words and addresses.

Versioning

Semantic versioning. The tool names and their output fields are the public contract; CHANGELOG.md marks anything you have to act on as Breaking.

Development

make check

That is what CI runs. docs/development.md says what each gate holds and how the live driver works.

Documentation

docs/README.md is the index. The design, the platform facts behind it and a verdict on every Gmail API method are in docs/architecture.md.

Contributing

See CONTRIBUTING.md.

Security

Report a vulnerability through a private advisory; see SECURITY.md.

Code of conduct

CODE_OF_CONDUCT.md.

License

Apache 2.0.