Gmail MCP

Gmail for your AI assistant — several accounts at once, on a server you own.

*日本語版 · 简体中文*

gmail-mcp connects Gmail to Claude and any other MCP client. It can search and read mail, send and reply-all with quoted history, forward, handle attachments and inline images, and manage drafts, labels, and threads — across several Google accounts at the same time.

It runs as a remote server on your own Cloudflare Worker, so the same connection answers from Claude Code on a laptop, claude.ai in a browser, and Claude on a phone. Each connection signs in to one Google account, and the Google refresh token stays in your Cloudflare account.

Two things push people here. The Gmail connectors built into Claude and Google read mail and write drafts, but cannot send, and hold one Google account per assistant account. Servers that can send are usually local processes — fine at a desk, invisible from a phone.

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How it compares

A longer comparison — six projects, twelve rows

| | gmail-mcp | Claude · Google built-in | taylorwilsdon/ google_workspace_mcp | ArtyMcLabin/ Gmail-MCP-Server | shinzo-labs/ gmail-mcp | aaronsb/ google-workspace-mcp | | :-- | :-: | :-: | :-: | :-: | :-: | :-: | | Where it runs | Cloudflare Workers | vendor-hosted | your server or local | local | local | local | | Reachable from a phone | ✅ | ✅ | ✅ | ❌ | ❌ | ❌ | | Several mailboxes at once | ✅ bound per connection | ❌ | ✅ chosen per call | ❌ aliases only | ❌ | ✅ chosen per call | | Send mail | ✅ | ❌ | ✅ | ✅ | ✅ | ✅ | | Attachments · inline cid: images | ✅ | undocumented | ✅ | ✅ | ❌ | ✅ | | Reply-all with quoted history | ✅ | ❌ | drafts only | no quoting | ❌ | ✅ | | Forward | ✅ | ❌ | ✅ | ❌ | ❌ | ✅ | | Honors each part's charset | ✅ | — | ❌ UTF-8 assumed | ❌ UTF-8 assumed | ❌ | ❌ | | Rejects CRLF header injection | ✅ | — | ✅ framework | ✅ strips | ❌ none | ✅ | | Mailbox settings (filters, vacation) | ❌ out of scope | ❌ | filters | filters | ✅ | ❌ | | Tool count | 24 | 11–16 | 14 (Gmail) | 30 | 64 | 11 | | Who holds your refresh token | you | vendor | you | you | you | you |

google_workspace_mcp is the most complete project here. It covers all of Workspace rather than Gmail alone, and it appends your Gmail signature and pulls attachments straight from a URL, neither of which gmail-mcp does. shinzo-labs/gmail-mcp reaches vacation responders, delegates, and S/MIME through its 64 tools; those live under gmail.settings.*, a scope gmail-mcp never requests, so they stay beyond its reach whatever happens to a grant.

Two design differences decide most of the rest. Routing accounts by a call argument lets one grant touch every connected mailbox, while binding the mailbox to the connection means a wrong argument reaches nothing. And on reading, the local servers decode every part as UTF-8: ISO-2022-JP and Shift_JIS mail arrives garbled, and long messages that Gmail stores as attachment blobs come back with an empty body.

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Deploy it

About ten minutes. You need a Cloudflare account, bun, and a Google account. A domain on the Cloudflare account is optional — without one the Worker answers on workers.dev.

1 · Create a Google OAuth client

PROJECT="gmail-mcp-$(openssl rand -hex 3)"

gcloud auth login gcloud projects create "$PROJECT" --name="gmail-mcp" gcloud config set project "$PROJECT" gcloud services enable gmail.googleapis.com

Google exposes no API for the next two steps, so they happen in the Cloud console:

• OAuth consent screen → *External*, then under Audience press Publish app. Left in Testing, Google expires every refresh token after 7 days and each connection dies with its token. Published, the app shows an unverified-app warning at sign-in and serves up to 100 accounts.
• Credentials → Create credentials → OAuth client ID → *Web application*, with https:// /callback as an authorized redirect URI. Keep the client ID and secret.

is the domain you point at the Worker, or the workers.dev hostname it gets otherwise. Deploying first and coming back to fill this in works — the guide the Worker serves at / shows the exact value.

2 · Deploy the Worker

The button copies the repository into your GitHub account, creates the KV namespace and the Durable Object, and asks for the four secrets. It deploys to workers.dev; a custom domain is attached afterwards under Settings → Domains & Routes.

From a terminal instead:

git clone https://github.com/mkpoli/gmail-mcp && cd gmail-mcp

bun install bun run setup

bun run setup asks which domain to answer on, creates or reuses the OAUTH_KV namespace, takes the client ID and secret, generates a cookie key, and deploys. Those first two answers land in wrangler.local.jsonc, which git ignores — wrangler.jsonc names no account's namespace and no one's domain, so a clone deploys anywhere. Re-running setup to rotate a single secret is safe.

3 · Connect a client

Leave the client ID and secret fields empty — MCP clients register themselves.

claude mcp add --transport http gmail-personal https://<your-host>/mcp

claude mcp add --transport http gmail-work https:// /mcp/work

Run /mcp in Claude Code to sign each connection in to its Google account. In claude.ai it is Settings → Connectors → Add custom connector with the same URL. Any single-segment label works after /mcp/, which is how one deployment serves several mailboxes to clients that reject two servers sharing a URL.

Your deployment serves this guide at https:// /.

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What it can do

📖 Read ✍️ Write 🏷 Organize

whoami

search_messages

get_message

get_thread

get_attachment

send_message

reply_all

forward_message

create_draft

update_draft

send_draft

delete_draft

list_drafts

stage_attachment_begin

stage_attachment_append

stage_attachment_finish

list_labels

create_label

update_label

delete_label

modify_labels

modify_thread_labels

batch_modify_messages

trash_message · untrash_message

trash_thread · untrash_thread

Messages leave the way a mail client sends them: plain text with an HTML alternative, file attachments, and inline images referenced by cid:, nested as multipart/mixed › multipart/related › multipart/alternative. Subjects and display names use RFC 2047, filenames use RFC 2231, so Japanese, Chinese, and emoji survive the trip.

reply_all reads the original's Reply-To, From, To, and Cc, drops your own address and any address you send mail as, answers from the one the sender wrote to, carries the References chain, and quotes the original in whichever parts you send. forward_message reproduces the forwarded envelope and can re-attach the original's files; when they cannot all go, nothing is sent.

create_draft with replyToMessageId writes the reply as a draft to edit before sending: it joins the original's thread, carries In-Reply-To and References, derives the reply-all recipients and the Re: subject, and quotes the original. update_draft changes only the fields it is given; recipients, text, files added by hand in any client, and the thread the draft answers are read back and kept. A file whose base64 will not fit through tool arguments is staged instead: stage_attachment_begin returns an upload URL that takes the raw bytes in one curl -T, stage_attachment_append takes base64 in chunks, and every attachments field accepts the resulting stagingId.

Reading is bounded on purpose: message and thread bodies have character budgets, a whole response has a byte ceiling, and an attachment is returned inline only while it stays small enough to read. A long mailing-list thread comes back trimmed with a note saying so rather than filling the assistant's context. A larger file comes back as a download link that works for an hour while the session stays open, and curl -o saves it to disk without its bytes passing through the conversation.

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How it works

Two OAuth flows meet in one Worker. The MCP client authenticates *to* the Worker; the Worker authenticates *to* Google on your behalf. Neither side holds the other's credentials.

sequenceDiagram

autonumber participant C as MCP client (Claude Code · claude.ai) participant W as Worker (OAuthProvider + McpAgent) participant G as Google (OAuth + Gmail API)

C->>W: POST /register (dynamic client registration) C->>W: GET /authorize (PKCE challenge) W->>C: approval dialog C->>G: consent screen — pick the account G->>W: GET /callback?code=… W->>W: allowlist check on the verified email W->>G: exchange code → access + refresh token W->>C: MCP access token (Google tokens sealed inside the grant) C->>W: POST /mcp — tools/call W->>G: Gmail REST (token refreshed as needed) G->>W: message / thread / label data W->>C: tool result

| 🔐 MCP-side OAuth | [workers-oauth-provider](https: