gws-mcp-server

Google Workspace for AI agents: Gmail, Calendar, Drive, Sheets, Docs, Slides, and Tasks as a curated set of 51 Model Context Protocol tools, built on the official Google Workspace CLI (gws).

Why?

The gws CLI had a built-in MCP server that was removed in v0.8.0 because it exposed 200-400 tools — causing context window bloat in MCP clients. This server takes a curated approach: you choose which Google services to expose, and only a focused set of high-value, narrowly scoped operations are registered as tools. Every tool declares all four MCP annotation hints — readOnlyHint, destructiveHint, idempotentHint, openWorldHint — so clients can reason about side effects, know which writes are safe to retry, and surface clearer consent prompts. This is the permissions leg of trust infrastructure for agents: a deliberately narrow tool surface, side effects declared on every tool, and no freestanding send tool — the only outbound email an agent can trigger is calendar invite/update notifications, opt-in via sendUpdates and off by default.

Prerequisites

• Node.js 18+
• gws CLI installed and authenticated (npm install -g @googleworkspace/cli && gws auth login)

Grant fewer scopes than the default

This server exposes no freestanding send tool — gmail_drafts_create explicitly does not send, and the only outbound email an agent can trigger is calendar invite/update notifications via sendUpdates, which is enum-validated and defaults to none. The token gws auth login mints is broader than that.

gws auth login opens a scope picker listing nine scopes. The default grant is seven: full read-write drive, spreadsheets, gmail.modify (Google documents it as "Read, compose, and send emails"), calendar, documents, presentations, and tasks — the same seven you get running non-interactively as DEFAULT_SCOPES.

The other two rows are Cloud Pub/Sub and Cloud Platform, and neither is part of the default grant — gws auth login --help describes --full as "Request all scopes incl. pubsub + cloud-platform."

Which rows start checked has not been verified against a live picker — the seven above are the documented default grant, not an observation of the TUI. Read the checkboxes before pressing Enter rather than trusting this paragraph.

So the token on disk can send mail and rewrite Drive even though nothing here will. Deselect what you do not need in the picker, or:

gws auth login --readonly    # read-only across services

-s gmail limits the picker to Gmail, per the flag's own help text ("Comma-separated service names to limit scope picker"). It cannot pull in cloud-platform or pubsub, because those two are reachable only through --full.

On Linux there is no keyring, and the encryption key is a file next to the data it encrypts. gws enables the keyring crate's native backends only for macOS and Windows; on every other platform the dependency is declared with no backend feature, so the store falls through to writing .encryption_key into ~/.config/gws/. That file is not a backup of a key held elsewhere — it is the key, and the credential store's own doc comment says it is never deleted. Setting GOOGLE_WORKSPACE_CLI_KEYRING_BACKEND=file changes nothing there because that is already the only path. On macOS and Windows the key file is removed once the OS keyring holds the key. If you run this headless on Linux, treat ~/.config/gws/ as a password file: anyone who can read the directory has the credentials.

Quick start

# Install
npm install -g gws-mcp-server

# Or run from source
git clone https://github.com/conorbronsdon/gws-mcp-server.git
cd gws-mcp-server
npm install && npm run build

Configuration

Claude Code (.mcp.json)

{
  "mcpServers": {
    "google-workspace": {
      "command": "npx",
      "args": [
        "gws-mcp-server",
        "--services", "drive,sheets,calendar,docs,slides,gmail,tasks"
      ]
    }
  }
}

Claude Desktop (claude_desktop_config.json)

{
  "mcpServers": {
    "google-workspace": {
      "command": "npx",
      "args": [
        "gws-mcp-server",
        "--services", "drive,sheets,calendar"
      ]
    }
  }
}

Options

--read-only

--read-only registers 22 tools instead of 51. Every tool that writes to Google is left unregistered, so it never appears in tools/list and there is nothing for an agent to call — including gmail_drafts_create, which is a write even though it never sends. drive_files_download stays, since it reads.

gws-mcp-server --read-only
gws-mcp-server --read-only --services drive,calendar   # combines with -s

This constrains the agent, not the credential. The token on disk keeps whatever scopes it was granted, and anything else on the machine can still use it. gws auth login --readonly is what narrows the token; the two are complementary. For an MCP server the agent is the threat model, but that is the limit of the claim.

Trimming context cost

Every registered tool rides along in each conversation: the full registry is roughly 37 KB of tools/list payload (~9.5K tokens) that your MCP client loads before anything else happens. The two flags above compose, and dropping whole services you don't use is the cheapest context win there is:

gws-mcp-server --services calendar                       # calendar assistant: 6 tools
gws-mcp-server --services drive,docs                     # document work, nothing else
gws-mcp-server --read-only --services drive,docs,sheets  # research setup: reads only

In .mcp.json or claude_desktop_config.json, the same trimming is just editing the args array:

"args": ["gws-mcp-server", "--services", "drive,calendar"]

A service's tool count (headers below) tracks its context cost: dropping tasks (12 tools) saves the most, docs (3 tools) the least. There is no per-tool exclude flag today — if service granularity is too coarse for your setup, open an issue describing the split you need.

Available services & tools

drive (14 tools)

• drive_files_list — Search and list files
• drive_files_get — Get file metadata
• drive_files_create — Create files (with optional upload)
• drive_files_copy — Copy files (useful for format conversion)
• drive_files_update — Update file metadata/content
• drive_files_delete — Delete files
• drive_files_export — Export Google Workspace files (Doc, Sheet, Slide) to other formats
• drive_files_download — Download file content (text inline, binary as base64 or saved to a path; Google-native files are exported to a readable format)
• drive_permissions_create — Share files
• drive_permissions_list — List all permissions on a file (audit sharing state, e.g. check for public access)
• drive_permissions_update — Change an existing permission's role (e.g. reader to writer); downgrades remove capabilities. Use the dedicated transfer tools below for ownership changes.
• drive_permissions_delete — Revoke a permission from a file
• drive_permissions_transferOwnership — Immediately transfer ownership to another Google Workspace account in the SAME organization, downgrading the current owner to writer; sends a mandatory notification email; not supported for shared drive files
• drive_permissions_proposeOwnershipTransfer — Propose transferring ownership between personal/consumer accounts; the recipient must separately accept (mandatory email notification), this doesn't transfer it outright

sheets (5 tools)

• sheets_get — Get spreadsheet metadata
• sheets_values_get — Read cell values
• sheets_values_update — Write cell values
• sheets_values_append — Append rows
• sheets_batchUpdate — Apply updates to a spreadsheet (conditional formatting, cell/border formatting, adding sheets, and more; delete requests are permanent)

calendar (6 tools)

• calendar_events_list — List events
• calendar_events_get — Get event details
• calendar_events_insert — Create events, optionally with attendees. sendUpdates controls invitation email (default none — no email, though the event may still appear on attendees' calendars depending on their settings)
• calendar_events_update — Update events (only supplied fields change — except attendees, which replaces the whole list; omitted attendees are uninvited). Same sendUpdates support as insert
• calendar_events_delete — Delete events
• calendar_freebusy_query — Query free/busy information for one or more calendars over a time range

docs (3 tools)

• docs_get — Get document content
• docs_create — Create documents
• docs_batchUpdate — Apply document updates

slides (5 tools)

• slides_get — Get a presentation's slides, layouts, masters, and page elements
• slides_create — Create a blank presentation
• slides_batchUpdate — Apply updates (insert/update/delete slides, text, shapes, tables, etc)
• slides_pages_get — Get a single page (slide, layout, or master)
• slides_pages_getThumbnail — Get a thumbnail image URL for a page

gmail (6 tools)

• gmail_messages_list — Search messages
• gmail_messages_get — Read a message
• gmail_threads_list — Search threads
• gmail_threads_get — Read a full thread
• gmail_threads_modify — Add/remove labels on a thread (archive, mark read, star)
• gmail_drafts_create — Create a draft (plain text and/or HTML, with reply threading via threadId). Drafts are never auto-sent

tasks (12 tools)

• tasks_tasklists_list — List task lists
• tasks_tasklists_get — Get a task list
• tasks_tasklists_insert — Create a task list
• tasks_tasklists_update — Update a task list (only supplied fields change)
• tasks_tasklists_delete — Delete a task list
• tasks_tasks_list — List tasks (filters: completed/hidden/due dates)
• tasks_tasks_get — Get a task
• tasks_tasks_insert — Create a task (optionally nested or positioned)
• tasks_tasks_update — Update a task (only supplied fields change; common use: mark complete)
• tasks_tasks_move — Move a task within/across lists or reorder
• tasks_tasks_delete — Delete a task
• tasks_tasks_clear — Hide all completed tasks in a list

Update semantics: the *_update tools (calendar events, tasks, task lists) use the Google API's patch verb — they merge the fields you supply and leave the rest untouched. To clear an existing value, pass it explicitly (e.g. an empty string) rather than omitting it.

Total: 51 tools (vs 200-400 in the old implementation)

Adding new tools

Edit src/services.ts to add tool definitions. Each tool maps directly to a gws CLI command:

{
  name: "drive_files_list",           // MCP tool name
  description: "List files in Drive", // Shown to AI
  command: ["drive", "files", "list"],// gws CLI args
  params: [                           // Maps to --params JSON
    { name: "q", description: "Search query", type: "string", required: false },
  ],
  bodyParams: [                       // Maps to --json body
    { name: "name", description: "File name", type: "string", required: true },
  ],
}

Typed errors

Tool call failures are mapped to a typed error hierarchy (src/errors.ts): AuthenticationError (401/403), RateLimitError (429), ValidationError (400), NotFoundError (404, with a shared-drive access hint for drive commands), and ServerError (5xx), all extending a base GwsError. Unlike an HTTP API client, this server has no response object to read a status code from — it spawns the gws CLI as a subprocess and only sees plain text (stdout/stderr, or a rejected promise's .message). mapGwsErrorToTyped() recovers a status-like code from that text, handling both a raw JSON error body (Google's own {"error":{"code":...,"message":...}} shape) and plain text containing an HTTP-status-like token (e.g. "Error 404: ..."). If neither pattern is found, the original message passes through unchanged rather than forcing an invented status onto it.

Architecture

MCP Client (Claude) ←→ stdio ←→ gws-mcp-server ←→ gws CLI ←→ Google APIs

The server is a thin wrapper: it translates MCP tool calls into gws CLI invocations, passes --params and --json as appropriate, and returns the JSON output. Authentication stays in the gws CLI — this server never sees or stores your Google credentials.

Development

git clone https://github.com/conorbronsdon/gws-mcp-server.git
cd gws-mcp-server
npm ci
npm run lint    # type-check
npm run build
npm test        # vitest, mocks the executor layer — no real gws calls

Contributing

Issues and pull requests are welcome. The most useful contributions are new tool definitions in src/services.ts for high-value gws operations (see "Adding new tools" above). Keep the curated contract: a focused set of narrowly scoped tools, not a 1:1 mirror of every Google API surface. See SECURITY.md for how to report vulnerabilities.

Other options

This server is deliberately narrow: a curated tool surface, side effects declared on every tool, no freestanding send tool. That is the right trade for some workflows and the wrong one for others. The real alternatives:

Worth saying plainly: Google's official Gmail MCP server is also draft-only, with no send tool — the curated-surface argument is no longer contrarian. What this server still does that those don't: Google Tasks (Google's official lineup has no Tasks server), all four MCP annotation hints on every tool, a local stdio server with no preview application or plan gating, and --read-only as a single flag.

The analytics siblings

These are separate credential families, not one login: Workspace authenticates with gws auth login, Search Console with a webmasters OAuth credential, YouTube Analytics with a yt-analytics.readonly OAuth credential, GA4 with Application Default Credentials scoped analytics.readonly. Nothing here shares a token with anything else.

About

Built and maintained by Conor Bronsdon. I host the Chain of Thought podcast, which covers AI infrastructure, developer tools, and how practitioners actually use this stuff. I built this to give the agent workflows that run the show safe, curated access to Gmail, Calendar, Drive, Sheets, Docs, Slides, and Tasks.

Companion tools:

• Transistor-MCP: the Transistor.fm MCP server. Episodes, transcripts, and download counts.
• substack-mcp: read posts and manage drafts on Substack, safe for agent workflows.
• podcastindex-mcp: the Podcast Index MCP server, search by person or topic, trending shows, feed health.
• op3-mcp: podcast analytics through OP3. Downloads, geography, apps. Read-only.
• ai-tools-for-creators: a curated list of AI skills and MCP servers for people who ship ideas for a living.

More at chainofthought.show and on X.

Disclaimer

This is an independent personal project, not affiliated with, sponsored by, or endorsed by any company. All views expressed are my own.

License

MIT