See it in action:

Overview

Workspace MCP is the single most complete MCP server that integrates all major Google Workspace services with AI assistants. It supports both single-user operation and multi-user authentication via OAuth 2.1, making it a powerful backend for custom applications. Built with FastMCP for optimal performance, featuring advanced authentication handling, service caching, and streamlined development patterns. The entire toolset is available for CLI usage supporting both local and remote instances.

Simplified Setup: can use Google Desktop OAuth clients for local runs - no redirect URIs or port configuration needed!

Features

12 services  —  Gmail · Drive · Calendar · Docs · Sheets · Slides · Forms · Chat · Apps Script · Tasks · Contacts · Search

Security & Compliance

Quick Start

Set credentials → pick a launch command → connect your client

# 1. Credentials
export GOOGLE_OAUTH_CLIENT_ID="..."
export GOOGLE_OAUTH_CLIENT_SECRET="..."

# 2. Launch — pick a tier
uvx workspace-mcp --tool-tier core       # essential tools
uvx workspace-mcp --tool-tier extended   # core + management ops
uvx workspace-mcp --tool-tier complete   # everything

# Or cherry-pick services
uv run main.py --tools gmail drive calendar

# 1. Credentials
export MCP_ENABLE_OAUTH21=true
export GOOGLE_OAUTH_CLIENT_ID="..."
export WORKSPACE_MCP_PORT=8000
export GOOGLE_OAUTH_REDIRECT_URI="http://localhost:${WORKSPACE_MCP_PORT}/oauth2callback"
export OAUTHLIB_INSECURE_TRANSPORT=1
# Leave GOOGLE_OAUTH_CLIENT_SECRET unset for public PKCE clients
export FASTMCP_SERVER_AUTH_GOOGLE_JWT_SIGNING_KEY="$(openssl rand -hex 32)"

# 2. Launch — OAuth 2.1 requires HTTP transport
uvx workspace-mcp --transport streamable-http --tool-tier core
uvx workspace-mcp --transport streamable-http --tool-tier extended
uvx workspace-mcp --transport streamable-http --tool-tier complete

# Or cherry-pick services
uv run main.py --transport streamable-http --tools gmail drive calendar

_{Credential setup → · All launch options → · Tier details →}

One-Click Claude Desktop Install

.dxt bundles server, deps & manifest — download → double-click → done. No terminal, no JSON editing.

1. Download the latest google_workspace_mcp.dxt from Releases
2. Install — double-click the file, Claude Desktop prompts to install
3. Configure — Settings → Extensions → Google Workspace MCP, paste your OAuth credentials
4. Use it — start a new Claude chat and call any Google Workspace tool

Prerequisites

Python 3.10+ · uv/uvx · Google Cloud Project with OAuth 2.0 credentials

If you want the GCS credential store backend, install the optional dependency first:

uv sync --extra gcs
# or
pip install "workspace-mcp[gcs]"

Configuration

Google Custom Search Setup

programmablesearchengine.google.com
/controlpanel/create

→ Configure sites or entire web
→ Note your Engine ID (cx)

developers.google.com
/custom-search/v1/overview

→ Create/select project
→ Enable Custom Search API
→ Create credentials (API Key)

export GOOGLE_PSE_API_KEY=\
  "your-api-key"
export GOOGLE_PSE_ENGINE_ID=\
  "your-engine-id"

Start the Server

📌 Transport Mode Guidance: Use streamable HTTP mode (--transport streamable-http) for all modern MCP clients including Claude Code, VS Code MCP, and MCP Inspector. Stdio mode is only for clients with incomplete MCP specification support.

uv run main.py

uv run main.py \
  --transport streamable-http

uv run main.py \
  --single-user

# Load specific services only
uv run main.py --tools gmail drive calendar
uv run main.py --tools sheets docs

# Combine with other flags
uv run main.py --single-user --tools gmail

# Requests only read-only scopes & disables write tools
uv run main.py --read-only

# Combine with specific tools or tiers
uv run main.py --tools gmail drive --read-only
uv run main.py --tool-tier core --read-only

# Per-service permission levels
uv run main.py --permissions gmail:organize drive:readonly

# Combine permissions with tier filtering
uv run main.py --permissions gmail:send drive:full --tool-tier core

uv run main.py --tool-tier core      # ● Essential tools only
uv run main.py --tool-tier extended  # ◐ Core + additional
uv run main.py --tool-tier complete  # ○ All available tools

docker build -t workspace-mcp .
docker run -p 8000:8000 -v $(pwd):/app \
  workspace-mcp --transport streamable-http

# With tool selection via environment variables
docker run -e TOOL_TIER=core workspace-mcp
docker run -e TOOLS="gmail drive calendar" workspace-mcp

CLI

The workspace-cli command lists tools and calls them against a running server — with encrypted, disk-backed OAuth token caching so you only authenticate once. On first run it opens a browser for Google consent; subsequent runs reuse the cached tokens automatically.

Tokens are stored encrypted at ~/.workspace-mcp/cli-tokens/ using a Fernet key auto-generated at ~/.workspace-mcp/.cli-encryption-key.

uv run workspace-cli list
uv run workspace-cli --url https://custom.server/mcp list

# Or, if installed globally:
workspace-cli list
workspace-cli --url https://custom.server/mcp list

uv run workspace-cli call search_gmail_messages \
  query="is:unread" max_results=5

fastmcp inspect fastmcp_server.py                        # print tools, resources, prompts
fastmcp install claude-code fastmcp_server.py             # one-command client setup
fastmcp install cursor fastmcp_server.py
fastmcp discover                                          # find servers configured in editors

Tool Tiers

The server organizes tools into three progressive tiers for simplified deployment. Choose a tier that matches your usage needs and API quota requirements.

Usage Examples

# Basic tier selection
uv run main.py --tool-tier core                            # Start with essential tools only
uv run main.py --tool-tier extended                        # Expand to include management features
uv run main.py --tool-tier complete                        # Enable all available functionality

# Selective service loading with tiers
uv run main.py --tools gmail drive --tool-tier core        # Core tools for specific services
uv run main.py --tools gmail --tool-tier extended          # Extended Gmail functionality only
uv run main.py --tools docs sheets --tool-tier complete    # Full access to Docs and Sheets

# Combine tier selection with granular permission levels
uv run main.py --permissions gmail:organize drive:full --tool-tier core

📋 Credential Configuration

export GOOGLE_OAUTH_CLIENT_ID=\
  "your-client-id"
export GOOGLE_OAUTH_CLIENT_SECRET=\
  "your-secret"

# Download & place in project root
client_secret.json

# Or specify custom path
export GOOGLE_CLIENT_SECRET_PATH=\
  /path/to/secret.json

cp .env.oauth21 .env
# Edit .env with credentials

🧰 Available Tools

Note: All tools support automatic authentication via @require_google_service() decorators with 30-minute service caching.

📅 Google Calendar _{calendar_tools.py}

📁 Google Drive _{drive_tools.py}

📧 Gmail _{gmail_tools.py}

attachments=[{"path": "/path/to/report.pdf"}]

attachments=[{
    "filename": "report.pdf",
    "content": "JVBERi0xLjQK...",  # base64-encoded
    "mime_type": "application/pdf"   # optional
}]

export WORKSPACE_ATTACHMENT_DIR="/path/to/custom/dir"

📝 Google Docs _{docs_tools.py}

📊 Google Sheets _{sheets_tools.py}

🖼️ Google Slides _{slides_tools.py}

📋 Google Forms _{forms_tools.py}

✓ Google Tasks _{tasks_tools.py}

👤 Google Contacts _{contacts_tools.py}

💬 Google Chat _{chat_tools.py}

🔍 Google Custom Search _{search_tools.py}

⚡ Google Apps Script _{apps_script_tools.py}

Connect to Claude Desktop

The server supports two transport modes:

Stdio Mode (Legacy - For Clients with Incomplete MCP Support)

⚠️ Important: Stdio mode is a legacy fallback for clients that don't properly implement the MCP specification with OAuth 2.1 and streamable HTTP support. Claude Code and other modern MCP clients should use streamable HTTP mode (--transport streamable-http) for proper OAuth flow and multi-user support.

In general, you should use the one-click DXT installer package for Claude Desktop. If you are unable to for some reason, you can configure it manually via claude_desktop_config.json

Manual Claude Configuration (Alternative)

{
  "mcpServers": {
    "google_workspace": {
      "command": "uvx",
      "args": ["workspace-mcp"],
      "env": {
        "GOOGLE_OAUTH_CLIENT_ID": "your-client-id",
        "GOOGLE_OAUTH_CLIENT_SECRET": "your-secret",
        "OAUTHLIB_INSECURE_TRANSPORT": "1"
      }
    }
  }
}

Connect to LM Studio

Add a new MCP server in LM Studio (Settings → MCP Servers) using the same JSON format:

{
  "mcpServers": {
    "google_workspace": {
      "command": "uvx",
      "args": ["workspace-mcp"],
      "env": {
        "GOOGLE_OAUTH_CLIENT_ID": "your-client-id",
        "GOOGLE_OAUTH_CLIENT_SECRET": "your-secret",
        "OAUTHLIB_INSECURE_TRANSPORT": "1",
      }
    }
  }
}

2. Advanced / Cross-Platform Installation

If you’re developing, deploying to servers, or using another MCP-capable client, keep reading.

Instant CLI (uvx)

# Requires Python 3.10+ and uvx
# First, set credentials (see Credential Configuration above)
uvx workspace-mcp --tool-tier core  # or --tools gmail drive calendar

Local Development Setup

# Install everything needed for linting, tests, and release tooling
uv sync --group dev

# Run the same linter that git hooks invoke automatically
uv run ruff check .

# Execute the full test suite (async fixtures require pytest-asyncio)
uv run pytest

OAuth 2.1 Support (Multi-User Bearer Token Authentication)

The server includes OAuth 2.1 support for bearer token authentication, enabling multi-user session management. OAuth 2.1 automatically reuses your existing GOOGLE_OAUTH_CLIENT_ID and, for confidential clients, GOOGLE_OAUTH_CLIENT_SECRET credentials - no additional Google-side configuration needed. Public PKCE clients are also supported: if you omit GOOGLE_OAUTH_CLIENT_SECRET, set FASTMCP_SERVER_AUTH_GOOGLE_JWT_SIGNING_KEY explicitly.

When to use OAuth 2.1:

• Multiple users accessing the same MCP server instance
• Need for bearer token authentication instead of passing user emails
• Building web applications or APIs on top of the MCP server
• Production environments requiring secure session management
• Browser-based clients requiring CORS support

⚠️ Important: Mutually exclusive authentication modes

OAuth 2.1 mode (MCP_ENABLE_OAUTH21=true) cannot be used together with --single-user or service account mode:

• Single-user mode: For legacy clients that pass user emails in tool calls
• OAuth 2.1 mode: For modern multi-user scenarios with bearer token authentication
• Service account mode: For headless/server-to-server use via domain-wide delegation

Choose one authentication method - combining incompatible modes will result in a startup error.

Enabling OAuth 2.1: To enable OAuth 2.1, set the MCP_ENABLE_OAUTH21 environment variable to true.

# OAuth 2.1 requires HTTP transport mode
export MCP_ENABLE_OAUTH21=true
uv run main.py --transport streamable-http

If MCP_ENABLE_OAUTH21 is not set to true, the server will use legacy authentication, which is suitable for clients that do not support OAuth 2.1.

# Public deployment — restrict to Claude's hosted OAuth callbacks
export WORKSPACE_MCP_ALLOWED_CLIENT_REDIRECT_URIS="https://claude.ai/api/mcp/auth_callback,https://claude.com/api/mcp/auth_callback"

# Add Claude Code CLI (loopback redirects on ephemeral ports)
export WORKSPACE_MCP_ALLOWED_CLIENT_REDIRECT_URIS="https://claude.ai/api/mcp/auth_callback,https://claude.com/api/mcp/auth_callback,http://localhost:*/callback,http://127.0.0.1:*/callback"

Stateless Mode (Container-Friendly)

The server supports a stateless mode designed for containerized environments where file system writes should be avoided:

Enabling Stateless Mode:

# Stateless mode requires OAuth 2.1 to be enabled
export MCP_ENABLE_OAUTH21=true
export WORKSPACE_MCP_STATELESS_MODE=true
uv run main.py --transport streamable-http

Key Features:

• No file system writes: Credentials are never written to disk
• No debug logs: File-based logging is completely disabled
• Memory-only sessions: All tokens stored in memory via OAuth 2.1 session store
• Container-ready: Perfect for Docker, Kubernetes, and serverless deployments
• Token per request: Each request must include a valid Bearer token

Requirements:

• Must be used with MCP_ENABLE_OAUTH21=true
• Incompatible with single-user mode
• Clients must handle OAuth flow and send valid tokens with each request

This mode is ideal for:

• Cloud deployments where persistent storage is unavailable
• Multi-tenant environments requiring strict isolation
• Containerized applications with read-only filesystems
• Serverless functions and ephemeral compute environments

MCP Inspector: No additional configuration needed with desktop OAuth client.

Claude Code: No additional configuration needed with desktop OAuth client.

OAuth Proxy Storage Backends

The server supports pluggable storage backends for OAuth proxy state management via FastMCP 2.13.0+. Choose a backend based on your deployment needs.

Available Backends:

Configuration:

# Memory storage (fast, no persistence)
export WORKSPACE_MCP_OAUTH_PROXY_STORAGE_BACKEND=memory

# Disk storage (persists across restarts)
export WORKSPACE_MCP_OAUTH_PROXY_STORAGE_BACKEND=disk
export WORKSPACE_MCP_OAUTH_PROXY_DISK_DIRECTORY=~/.fastmcp/oauth-proxy

# Valkey/Redis storage (distributed, multi-server)
export WORKSPACE_MCP_OAUTH_PROXY_STORAGE_BACKEND=valkey
export WORKSPACE_MCP_OAUTH_PROXY_VALKEY_HOST=redis.example.com
export WORKSPACE_MCP_OAUTH_PROXY_VALKEY_PORT=6379

Disk support requires workspace-mcp[disk] (or py-key-value-aio[disk]) when installing from source. The official Docker image includes the disk extra by default. Valkey support is optional. Install workspace-mcp[valkey] (or py-key-value-aio[valkey]) only if you enable the Valkey backend. Windows: building valkey-glide from source requires MSVC C++ build tools with C11 support. If you see aws-lc-sys C11 errors, set CFLAGS=/std:c11.

External OAuth 2.1 Provider Mode

The server supports an external OAuth 2.1 provider mode for scenarios where authentication is handled by an external system. In this mode, the MCP server does not manage the OAuth flow itself but expects valid bearer tokens in the Authorization header of tool calls.

Enabling External OAuth 2.1 Provider Mode:

# External OAuth provider mode requires OAuth 2.1 to be enabled
export MCP_ENABLE_OAUTH21=true
export EXTERNAL_OAUTH21_PROVIDER=true
uv run main.py --transport streamable-http

How It Works:

• Protocol-level auth enabled: All MCP requests (including initialize and tools/list) require a valid Bearer token, following the standard OAuth 2.1 flow. Unauthenticated requests receive a 401 with resource metadata pointing to Google's authorization server.
• External OAuth flow: Your external system handles the OAuth flow and obtains Google access tokens (ya29.*)
• Token validation: Server validates bearer tokens by calling Google's userinfo API
• Multi-user support: Each request is authenticated independently based on its bearer token
• Resource metadata discovery: The server serves /.well-known/oauth-protected-resource (RFC 9728) advertising Google as the authorization server and the required scopes

Key Features:

• No local OAuth flow: Server does not provide /authorize, /token, or /register endpoints — only resource metadata
• Bearer token only: All authentication via Authorization: Bearer <token> headers
• Stateless by design: Works seamlessly with WORKSPACE_MCP_STATELESS_MODE=true
• External identity providers: Integrate with your existing authentication infrastructure

Requirements:

• Must be used with MCP_ENABLE_OAUTH21=true
• OAuth client ID still required for token validation; client secret is optional for public clients (GOOGLE_OAUTH_CLIENT_ID, optional GOOGLE_OAUTH_CLIENT_SECRET)
• External system must obtain valid Google OAuth access tokens (ya29.*)
• Each tool call request must include valid bearer token

Use Cases:

• Integrating with existing authentication systems
• Custom OAuth flows managed by your application
• API gateways that handle authentication upstream
• Multi-tenant SaaS applications with centralized auth
• Mobile or web apps with their own OAuth implementation

Service Account Mode (Domain-Wide Delegation)

WARNING: This mode uses Google Workspace domain-wide delegation, which grants the service account the ability to impersonate any user in your domain for the configured scopes. This is powerful and dangerous — do not use this unless you fully understand the security implications. A misconfigured service account with broad scopes can read, modify, and delete data across every user in your organization. Only use this in tightly controlled environments where you know exactly what you're doing.

Service account mode allows the server to authenticate using a Google Cloud service account with domain-wide delegation instead of interactive OAuth flows. The service account impersonates a single configured domain user for all API calls.

When to use service account mode:

• Headless or unattended environments where no browser is available for OAuth consent
• Server-to-server integrations that need to act on behalf of a specific domain user
• CI/CD pipelines or automation scripts
• Environments where you cannot or do not want to manage per-user OAuth tokens

Enabling Service Account Mode:

# Option 1: Key file on disk
export GOOGLE_SERVICE_ACCOUNT_KEY_FILE="/path/to/service-account-key.json"
export USER_GOOGLE_EMAIL="[email protected]"
uv run main.py

# Option 2: Inline JSON key (e.g., from a secret manager)
export GOOGLE_SERVICE_ACCOUNT_KEY_JSON='{"type":"service_account","project_id":"...","private_key":"...","client_email":"..."}'
export USER_GOOGLE_EMAIL="[email protected]"
uv run main.py

Prerequisites:

1. A Google Cloud service account with a JSON key
2. Domain-wide delegation enabled for the service account in your Google Workspace Admin Console (Security → API controls → Domain-wide delegation)
3. The required OAuth scopes authorized for the service account's client ID in the Admin Console
4. USER_GOOGLE_EMAIL set to the domain user the service account will impersonate

Incompatibilities:

• Cannot be combined with --single-user mode
• Cannot be combined with MCP_ENABLE_OAUTH21=true
• Only one key source may be provided — set either GOOGLE_SERVICE_ACCOUNT_KEY_FILE or GOOGLE_SERVICE_ACCOUNT_KEY_JSON, not both

Key Behaviors:

• The OAuth callback server is not started (no interactive auth needed)
• Credentials directory permission checks are skipped
• All operations impersonate the configured USER_GOOGLE_EMAIL — any email addresses supplied in tool calls (e.g., user_email parameters) are ignored. This differs from OAuth modes where each user authenticates separately.
• The service account key is validated at startup (checks for required fields and correct type)

VS Code MCP Client Support

✅ Recommended: VS Code MCP extension properly supports the full MCP specification. Always use HTTP transport mode for proper OAuth 2.1 authentication.

{
    "servers": {
        "google-workspace": {
            "url": "http://localhost:8000/mcp/",
            "type": "http"
        }
    }
}

Claude Code MCP Client Support

✅ Recommended: Claude Code is a modern MCP client that properly supports the full MCP specification. Always use HTTP transport mode with Claude Code for proper OAuth 2.1 authentication and multi-user support.

# Start the server in HTTP mode first
uv run main.py --transport streamable-http

# Then add to Claude Code
claude mcp add --transport http workspace-mcp http://localhost:8000/mcp

# Optional: install the bundled Claude skill for better Workspace tool routing
mkdir -p ~/.claude/skills
ln -s "$(pwd)/skills/managing-google-workspace" ~/.claude/skills/managing-google-workspace

Reverse Proxy Setup

If you're running the MCP server behind a reverse proxy (nginx, Apache, Cloudflare, etc.), you have two configuration options:

Problem: When behind a reverse proxy, the server constructs OAuth URLs using internal ports (e.g., http://localhost:8000) but external clients need the public URL (e.g., https://your-domain.com).

Solution 1: Set WORKSPACE_EXTERNAL_URL for all OAuth endpoints:

# This configures all OAuth endpoints to use your external URL
export WORKSPACE_EXTERNAL_URL="https://your-domain.com"

Solution 2: Set GOOGLE_OAUTH_REDIRECT_URI for just the callback:

# This only overrides the OAuth callback URL
export GOOGLE_OAUTH_REDIRECT_URI="https://your-domain.com/oauth2callback"

You also have options for: | OAUTH_CUSTOM_REDIRECT_URIS (optional) | Comma-separated list of additional redirect URIs | | OAUTH_ALLOWED_ORIGINS (optional) | Comma-separated list of additional CORS origins |

Important:

• Use WORKSPACE_EXTERNAL_URL when all OAuth endpoints should use the external URL (recommended for reverse proxy setups)
• Use GOOGLE_OAUTH_REDIRECT_URI when you only need to override the callback URL
• The redirect URI must exactly match what's configured in your Google Cloud Console
• Your reverse proxy must forward OAuth-related requests (/oauth2callback, /oauth2/*, /.well-known/*) to the MCP server

# Configure credentials first (see Credential Configuration section)

# Start with specific tools only
uvx workspace-mcp --tools gmail drive calendar tasks

# Start with tool tiers (recommended for most users)
uvx workspace-mcp --tool-tier core      # Essential tools
uvx workspace-mcp --tool-tier extended  # Core + additional features
uvx workspace-mcp --tool-tier complete  # All tools

# Start in HTTP mode for debugging
uvx workspace-mcp --transport streamable-http

Requires Python 3.10+ and uvx. The package is available on PyPI.

Development Installation

For development or customization:

git clone https://github.com/taylorwilsdon/google_workspace_mcp.git
cd google_workspace_mcp
uv run main.py

Development Installation (For Contributors):

{
  "mcpServers": {
    "google_workspace": {
      "command": "uv",
      "args": [
        "run",
        "--directory",
        "/path/to/repo/google_workspace_mcp",
        "main.py"
      ],
      "env": {
        "GOOGLE_OAUTH_CLIENT_ID": "your-client-id",
        "GOOGLE_OAUTH_CLIENT_SECRET": "your-secret",
        "OAUTHLIB_INSECURE_TRANSPORT": "1"
      }
    }
  }
}

HTTP Mode (For debugging or web interfaces)

If you need to use HTTP mode with Claude Desktop:

{
  "mcpServers": {
    "google_workspace": {
      "command": "npx",
      "args": ["mcp-remote", "http://localhost:8000/mcp"]
    }
  }
}

Note: Make sure to start the server with --transport streamable-http when using HTTP mode.

First-Time Authentication

The server uses Google Desktop OAuth for simplified authentication:

• No redirect URIs needed: Desktop OAuth clients handle authentication without complex callback URLs
• Automatic flow: The server manages the entire OAuth process transparently
• Transport-agnostic: Works seamlessly in both stdio and HTTP modes

When calling a tool:

1. Server returns authorization URL
2. Open URL in browser and authorize
3. Google provides an authorization code
4. Paste the code when prompted (or it's handled automatically)
5. Server completes authentication and retries your request

◆ Development

Project Structure

google_workspace_mcp/
├── auth/              # Authentication system with decorators
├── core/              # MCP server and utilities
├── g{service}/        # Service-specific tools
├── main.py            # Server entry point
├── client_secret.json # OAuth credentials (not committed)
└── pyproject.toml     # Dependencies

Adding New Tools

from auth.service_decorator import require_google_service

@require_google_service("drive", "drive_read")  # Service + scope group
async def your_new_tool(service, param1: str, param2: int = 10):
    """Tool description"""
    # service is automatically injected and cached
    result = service.files().list().execute()
    return result  # Return native Python objects

Architecture Highlights

• Service Caching: 30-minute TTL reduces authentication overhead
• Scope Management: Centralized in SCOPE_GROUPS for easy maintenance
• Error Handling: Native exceptions instead of manual error construction
• Multi-Service Support: @require_multiple_services() for complex tools

Credential Store System

The server includes an abstract credential store API with pluggable backends for managing Google OAuth credentials:

Features:

• Abstract Interface: CredentialStore base class defines standard operations (get, store, delete, list users)
• Local File Storage: LocalDirectoryCredentialStore — plaintext JSON files protected by filesystem permissions (0o600 / 0o700)
• GCS-Backed Storage: GCSCredentialStore — stores each user's credentials as an object in a Google Cloud Storage bucket. Supports atomic read-modify-write via generation preconditions, first-class Cloud IAM / Audit Logs integration, and transparent bucket-level CMEK encryption at rest
• Configurable Storage: Environment variables select backend and location
• Multi-User Support: Store and manage credentials for multiple Google accounts
• Automatic Directory Creation: Storage directory is created automatically if it doesn't exist (local backend)

Configuration:

# Install the optional dependency if you plan to use the GCS backend:
# uv sync --extra gcs
# or: pip install "workspace-mcp[gcs]"
#
# Select backend (default: local_directory). Supported: local_directory, gcs
export WORKSPACE_MCP_CREDENTIAL_STORE_BACKEND="gcs"

# --- local_directory options ---
export WORKSPACE_MCP_CREDENTIALS_DIR="/path/to/credentials"
# Backward-compatible alias:
export GOOGLE_MCP_CREDENTIALS_DIR="/path/to/credentials"

# Default directory locations (if no directory env var is set):
# - ~/.google_workspace_mcp/credentials (if home directory accessible)
# - ./.credentials (fallback)

# --- gcs options ---
export WORKSPACE_MCP_GCS_BUCKET="my-workspace-mcp-tokens"   # required
export WORKSPACE_MCP_GCS_PREFIX="credentials/"              # optional
export WORKSPACE_MCP_GCS_REQUIRE_CMEK="true"                # optional; see below

Backend selection:

• local_directory (default): Plaintext JSON records. Suitable for local development and single-user stdio mode. Existing pre-URL-encoding local credential filenames remain readable during migration; new writes use the URL-encoded filename mapping unless a legacy file already exists for that user.
• gcs: Stores credentials as objects in a GCS bucket using the JSON API. Authenticates via Application Default Credentials — on Cloud Run this means the runtime service account needs roles/storage.objectUser (or equivalent) on the bucket. Does not support list_users() — designed for multi-user OAuth 2.1 mode where users are looked up individually by email.

CMEK enforcement (gcs backend):

By default GCS encrypts objects with Google-managed keys. For customer-managed encryption, set a default KMS key on the bucket (e.g. via Terraform's google_storage_bucket.encryption.default_kms_key_name). All credentials written to the bucket will inherit the key transparently — no application-level key to manage.

To guard against accidentally deploying against a bucket without CMEK, set WORKSPACE_MCP_GCS_REQUIRE_CMEK=true. The store will verify the bucket has a default KMS key at startup and refuse to initialize otherwise. Note that this check reads bucket metadata, so the runtime service account additionally needs storage.buckets.get — grant roles/storage.bucketViewer on the bucket (or a custom role containing storage.buckets.get) in addition to the object-level role. roles/storage.objectUser alone covers only object operations.

Usage Example:

from auth.credential_store import get_credential_store, LocalDirectoryCredentialStore

# Get the global credential store instance
store = get_credential_store()

# Store credentials for a user
store.store_credential("[email protected]", credentials)

# Retrieve credentials
creds = store.get_credential("[email protected]")

# List all users with stored credentials (local_directory backend only;
# GCSCredentialStore intentionally does not support enumeration — use the
# upstream identity provider to enumerate users instead).
if isinstance(store, LocalDirectoryCredentialStore):
    users = store.list_users()

The credential store automatically handles credential serialization, expiry parsing, and provides error handling for storage operations.

⊠ Security

• Prompt Injection: This MCP server has the capability to retrieve your email, calendar events and drive files. Those emails, events and files could potentially contain prompt injections - i.e. hidden white text that tells it to forward your emails to a different address. You should exercise caution and in general, only connect trusted data to an LLM!
• Credentials: Never commit .env, client_secret.json or the .credentials/ directory to source control!
• OAuth Callback: Uses http://localhost:8000/oauth2callback for development (requires OAUTHLIB_INSECURE_TRANSPORT=1). If another process is already using port 8000, set WORKSPACE_MCP_PORT to a free port to avoid conflicts — e.g. export WORKSPACE_MCP_PORT=8123. If you use a web/confidential OAuth client (not the recommended Desktop client), also update the redirect URI in Google Cloud Console to match the new port (e.g. http://localhost:8123/oauth2callback); Desktop and PKCE clients do not require this.
• Transport-Aware Callbacks: Stdio mode starts a minimal HTTP server only for OAuth, ensuring callbacks work in all modes
• Production: Use HTTPS & OAuth 2.1 and configure accordingly
• Scope Minimization: Tools request only necessary permissions
• Local File Access Control: Tools that read local files (e.g., attachments, file:// uploads) are restricted to the managed attachment directory by default. Override this with the ALLOWED_FILE_DIRS environment variable if you intentionally need broader access:

  # Colon-separated list of directories (semicolon on Windows) from which local file reads are permitted
  export ALLOWED_FILE_DIRS="/home/user/documents:/data/shared"
  

  The managed attachment directory is controlled by WORKSPACE_ATTACHMENT_DIR and remains allowed even when ALLOWED_FILE_DIRS is set. Regardless of the allowlist, access to sensitive paths (.env, .ssh/, .aws/, /etc/shadow, credential files, etc.) is always blocked.
• Indirect Prompt Injection: In agentic clients, email bodies, documents, and calendar events can contain malicious instructions that try to coerce the model into exfiltrating local files. Do not broaden ALLOWED_FILE_DIRS unless you trust the client, the model behavior, and the data sources it can read.

≡ License

MIT License - see LICENSE file for details.

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