Samarth GTM MCP Server

A production-ready Model Context Protocol (MCP) server for the Google Tag Manager API v2, built for Samarth Analytics.

Use it through Samarth Desktop - the local Electron app with a chat UI that embeds this server (Quick Start). Full, guarded access to GTM: read workspace contents, create/update tags/triggers/variables, audit implementations, publish versions, and more.

New: browser portal with live QC audit. A white-label, browser-based customer experience lives in apps/portal/. Customers sign in with Google OAuth, pick a GTM account/container/workspace, and run a live, read-only QC audit. Publishes still require Samarth approval. See the portal README for OAuth setup; run with npm run portal:dev.

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Table of Contents

1. Features
2. Quick Start
3. Google Cloud OAuth Setup
4. Service Account Limitations
5. Environment Variables Reference
6. Guardrails
7. Available Tools
8. Cloud Deployment
9. Security Notes
10. Development
11. Releases
12. Troubleshooting

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Features

• Full GTM API v2 surface — accounts, containers, workspaces, tags, triggers, variables, folders, built-in variables, versions, sync, publish, preview
• Server-side & advanced GTM coverage — environments, user permissions, destinations, clients, transformations, zones, custom templates, gtag config, plus container snippet/lookup/combine/move-tag-id and workspace change-diff status
• GA4 coverage — GA4 Admin tools (ga4_*) plus GA4 Data API reporting (ga4_run_report, ga4_run_realtime_report) for intent-vs-reality reconciliation. Reads and reporting need only analytics.readonly; the GA4 Admin write tools are off by default behind GA4_MCP_ENABLE_WRITES / GA4_MCP_ENABLE_DELETES and additionally need analytics.edit
• Automatic pagination — every paginated list tool transparently follows nextPageToken to return all results, with optional maxPages/pageToken bounds
• Retry with exponential backoff + jitter — transient Google API failures (HTTP 408/429/5xx, network errors) on read requests are retried automatically; mutations are never auto-retried (tunable via GTM_MCP_RETRY_*)
• Two transport modes: stdio (local, for Claude Desktop/Cursor) and Streamable HTTP (cloud/team)
• Guardrails by default: read-only unless explicitly enabled; publish and delete gated separately
• Dry-run mode: simulate all writes without touching the API
• confirm=true required on all write/delete/publish operations
• Audit tool: inspects workspace for common GA4/GTM implementation issues
• Export tool: full workspace dump as structured JSON
• Zod schema validation on all inputs
• Detailed Google API error messages surfaced to the MCP client

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Quick Start

The way to run Samarth is the desktop app - a local Electron app with a chat UI that embeds the MCP server in-process. Multi-account Google sign-in, per-account LLM keys (OpenAI / Anthropic / Gemini), secrets in the OS keychain. Nothing to configure by hand: the Google OAuth client and your LLM key are entered in the app on first run.

You need: Node.js 18 or newer, Git, and a free Google "Desktop app" OAuth client - two values you create once in your Google Cloud project (exact click-by-click steps).

git clone https://github.com/samarthanalytics-sj/samarth-analytics-mcp.git
cd samarth-analytics-mcp/apps/desktop
npm install    # downloads the Electron binary (~100 MB first time)
npm run dev

The window opens; paste your OAuth client ID + secret and an LLM API key when asked, sign in to Google, and start chatting with your GTM / GA4 setup.

Prefer a config file over typing in the app? Put the OAuth client in a .env file instead - the app reads it on launch (values typed in the app and real shell variables always take precedence):

GOOGLE_DESKTOP_CLIENT_ID=your-client-id.apps.googleusercontent.com
GOOGLE_DESKTOP_CLIENT_SECRET=your-client-secret

Save it as apps/desktop/.env or at the repo root (already gitignored - never commit it). A repo-root .env using the server's GOOGLE_OAUTH_CLIENT_ID / GOOGLE_OAUTH_CLIENT_SECRET names works too, so one file can serve both the app and the MCP server. A packaged install reads .env from its data directory instead (%APPDATA% on Windows).

Your everyday launch afterwards is just:

cd samarth-analytics-mcp/apps/desktop && npm run dev

Full guide - Windows/macOS specifics, first-run setup, building a real .exe/.dmg installer, and the Error: Electron uninstall fix: apps/desktop/INSTALL.md.

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Google Cloud OAuth Setup

Step 1: Enable the GTM API

1. Go to Google Cloud Console
2. Select or create a project
3. Navigate to APIs & Services → Library
4. Search for "Tag Manager API" and click Enable
5. Search for "Google Analytics Admin API" and click Enable (required for the read-only ga4_* Admin tools)
6. Search for "Google Analytics Data API" and click Enable (required for ga4_run_report / ga4_run_realtime_report)

Step 2: Create OAuth 2.0 Credentials

1. Go to APIs & Services → Credentials
2. Click Create Credentials → OAuth 2.0 Client ID
3. Choose application type:
   • Desktop app — simplest for local stdio use (no redirect URI needed)
   • Web application — for the HTTP server (add your redirect URI)
4. Download the JSON or copy the Client ID and Client Secret
5. Add to .env:

   GOOGLE_CLIENT_ID=your-client-id.apps.googleusercontent.com
   GOOGLE_CLIENT_SECRET=your-client-secret
   GOOGLE_REDIRECT_URI=http://localhost:3001/oauth/callback
   

Step 3: Configure OAuth Consent Screen

1. Go to APIs & Services → OAuth consent screen
2. Choose External (or Internal if you have Google Workspace)
3. Fill in App name, support email
4. Add scopes:
   • https://www.googleapis.com/auth/tagmanager.readonly
   • https://www.googleapis.com/auth/tagmanager.edit.containers
   • https://www.googleapis.com/auth/tagmanager.edit.containerversions
   • https://www.googleapis.com/auth/tagmanager.manage.accounts
   • https://www.googleapis.com/auth/tagmanager.manage.users
   • https://www.googleapis.com/auth/tagmanager.publish
   • https://www.googleapis.com/auth/analytics.readonly (read-only GA4 Admin and Data API tools)
   • https://www.googleapis.com/auth/analytics.edit (GA4 Admin write tools — gated by GA4_MCP_ENABLE_WRITES)
   • https://www.googleapis.com/auth/analytics.manage.users (GA4 access-binding write tools)
5. Add your Google account as a test user (while the app is in "testing" mode)

Note: For personal/agency use, keeping the app in "Testing" mode is fine. You will need to re-authorize every 7 days unless you publish the app or get it verified.

Step 4: Run OAuth Setup

npm run auth:google

Or, if you prefer the older paste-the-code helper:

npm run oauth:setup

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Service Account Limitations

Short version: Service accounts do NOT work with GTM by default. Use OAuth 2.0.

The Google Tag Manager API is a user-data API — it manages resources owned by individual Google accounts. Service accounts are not Google users and are not automatically granted access to GTM containers.

Option A: Add the service account as a GTM user (simplest)

If you still want to use a service account:

1. Get the service account email (e.g., my-sa@project.iam.gserviceaccount.com)
2. In GTM, go to Admin → User Management at the account or container level
3. Add the service account email with the appropriate role (Read, Edit, Approve, Publish)
4. Set GOOGLE_SERVICE_ACCOUNT_KEY_FILE=/path/to/key.json in .env

Caveats: This only works if the GTM container is associated with a Google account, not a Google Workspace that restricts external sharing.

Option B: Domain-Wide Delegation (Google Workspace only)

For Google Workspace organizations:

1. Create a service account with a JSON key
2. Enable Domain-Wide Delegation on the service account in Google Cloud Console
3. In Google Workspace Admin Console → Security → API Controls → Domain-wide Delegation:
   • Add the service account client ID
   • Add scopes: https://www.googleapis.com/auth/tagmanager.edit.containers (and others as needed)
4. In .env, set:

   GOOGLE_SERVICE_ACCOUNT_KEY_FILE=/path/to/key.json
   

5. The server will impersonate the user automatically if you set a subject in buildGoogleAuth()

Caveats: Requires a paid Google Workspace account. Only available for your own domain.

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Environment Variables Reference

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Guardrails

The server enforces three independent guardrails in addition to the confirm=true requirement:

confirm=true is always required on write/delete/publish tools regardless of env settings. This prevents accidental modifications even when guardrails are enabled.

Recommended Configurations

Read-only exploration (default — safe for sharing with team):

GTM_MCP_ENABLE_WRITES=false
GTM_MCP_ENABLE_PUBLISH=false
GTM_MCP_ENABLE_DELETES=false

Development workspace edits (no publishing):

GTM_MCP_ENABLE_WRITES=true
GTM_MCP_ENABLE_PUBLISH=false
GTM_MCP_ENABLE_DELETES=false

Full access (use with care):

GTM_MCP_ENABLE_WRITES=true
GTM_MCP_ENABLE_PUBLISH=true
GTM_MCP_ENABLE_DELETES=true

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Available Tools

Accounts

Containers

Destinations

Workspaces

Tags

Triggers

Variables

Folders

Built-In Variables

Versions

Environments

User Permissions (account-level)

Server-Side & Advanced Container Resources

These are workspace-scoped resources from GTM API v2. Create/update accept the full resource as a JSON string (bodyJson) since their bodies are deeply nested. Each supports *_list (auto-paginated), *_get, *_create ✏️, *_update ✏️, *_delete 🗑️, and (except gtag_config) *_revert ✏️.

Analytics & Export

GA4 Admin (read-only)

Read-only wrappers over the Google Analytics Admin API (v1beta, with a single v1alpha call for enhanced measurement). These never write, update, or delete GA4 resources and require no confirm flag. They power the senior audit framework's GA4_ADMIN checks (custom dimensions/metrics, data streams & measurement IDs, data retention, enhanced measurement, key events, Google Ads links).

Requires the https://www.googleapis.com/auth/analytics.readonly scope and the Google Analytics Admin API enabled in your Google Cloud project. A 403 mentioning scope means you should re-run npm run auth:google.

Accepts either a bare numeric ID (123456789) or the fully-qualified form (properties/123456789, accounts/123456) wherever a property/account is required.

Documented limitations (not exposed by the GA4 Admin API v1beta, so intentionally not implemented rather than faked):

• Internal-traffic / unwanted-referral data filters — no public dataFilters collection; configured per data stream.
• Referral exclusions — no dedicated Admin API resource.
• Channel groups and audiences — exist only on the v1alpha surface and are out of scope for this read-only v1beta set.

GA4 Data API (read-only reporting)

Read-only wrappers over the Google Analytics Data API (v1beta). They never write and require no confirm flag. Use them to reconcile intent vs. reality — comparing the events a container is configured to send against the events GA4 actually reports (zero reported activity for a configured event is a red flag).

These use the same https://www.googleapis.com/auth/analytics.readonly scope as the GA4 Admin tools, so no extra consent is needed. Enable the Google Analytics Data API in your Google Cloud project.

Documented gaps (intentionally not exposed rather than faked): pivot reports, cohorts, and funnels.

Pagination

All list tools backed by paginated GTM endpoints (accounts_*-scoped containers, workspaces, tags, triggers, variables, folders, folder entities, environments, user permissions, clients, transformations, zones, templates, gtag configs) auto-follow pagination and return all results by default. Optional arguments:

• maxPages — cap the number of API pages fetched (default 50). If more pages remain, the response includes "truncated": true and a nextPageToken.
• pageToken — resume from a previous truncated result.

Non-truncated responses keep the original { <key>: [...], count } shape unchanged.

Two tools differ, because one list key does not describe what they return:

• folders_entities returns three parallel collections (tag, trigger, variable, always present, empty when the folder has none) plus a counts object, and adds truncated / nextPageToken only when the page ceiling was hit.
• export_container pages five collections independently, so it takes maxPages (applied per collection) but no pageToken. A short export is marked incomplete: true with truncatedCollections, per-collection nextPageTokens and a warning — in every format, including the default summary.

Legend: ✏️ requires GTM_MCP_ENABLE_WRITES=true | 🗑️ requires GTM_MCP_ENABLE_DELETES=true | 🚀 requires GTM_MCP_ENABLE_PUBLISH=true

All ✏️ 🗑️ 🚀 tools also require confirm: true in the tool arguments.

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Cloud Deployment

Transport

For cloud deployments, use GTM_MCP_TRANSPORT=http. The server exposes:

• POST /mcp — Streamable HTTP MCP endpoint
• GET /mcp — SSE stream for existing sessions
• DELETE /mcp — Session termination
• GET /health — Health check

There is no /oauth/callback route on this server. npm run auth:google runs its own short-lived listener on 127.0.0.1:3001 for the redirect; an unauthenticated callback on the hosted transport could overwrite the server's stored Google credentials, so it was removed.

Connecting Remote Clients

Clients that support Streamable HTTP can connect directly to the /mcp endpoint. For clients that only support stdio (like Claude Desktop), use mcp-remote as a proxy:

{
  "mcpServers": {
    "samarth-gtm-remote": {
      "command": "npx",
      "args": ["mcp-remote@next", "https://your-server.com/mcp"]
    }
  }
}

Vercel

Limitation: Vercel Serverless Functions have a 10-second timeout (hobby) / 60-second (pro). Stateful SSE sessions require persistent connections which Vercel does not support well. Use Vercel only for stateless MCP interactions. Recommended alternative: Vercel + external session store (Redis/Upstash), or use Render/Fly.io instead.

For Vercel, export the Express app as a serverless handler:

// api/mcp.ts
export default app; // where app is the Express instance

Set env vars in Vercel Dashboard → Settings → Environment Variables.

Render

1. Create a new Web Service in Render
2. Connect your GitHub repo
3. Build command: npm install && npm run build
4. Start command: GTM_MCP_TRANSPORT=http node dist/index.js
5. Add environment variables in Render Dashboard
6. Important: Set RENDER=true env var and ensure your health check hits /health

Render supports persistent long-lived connections — recommended for SSE/streaming.

Fly.io

fly launch
fly secrets set GOOGLE_CLIENT_ID=xxx GOOGLE_CLIENT_SECRET=xxx GOOGLE_REFRESH_TOKEN=xxx
fly secrets set GTM_MCP_TRANSPORT=http GTM_MCP_HTTP_PORT=3001
fly deploy

Fly.io has no request timeout limitations and supports persistent WebSocket/SSE connections. Recommended for production.

Docker

FROM node:20-alpine
WORKDIR /app
COPY package*.json ./
RUN npm ci --omit=dev
COPY dist/ ./dist/
ENV GTM_MCP_TRANSPORT=http
ENV GTM_MCP_HTTP_PORT=3001
EXPOSE 3001
CMD ["node", "dist/index.js"]

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Security Notes

1. Never commit .env — it contains OAuth tokens. .env is already in .gitignore.

2. Rotate tokens regularly — OAuth refresh tokens are long-lived but can be revoked. Revoke at myaccount.google.com/permissions.

3. Minimum scopes — If you only need read access, revoke write scopes by removing them from the OAuth consent screen and re-authorizing. The server reads fine with tagmanager.readonly only.

4. Cloud deployment: Store secrets in your platform's secret manager (Render Secrets, Fly.io Secrets, Vercel Env Vars), never in code or Docker images.

5. HTTP transport: /mcp has two built-in auth modes — GTM_MCP_HTTP_AUTH_TOKEN (one shared bearer token, identifies the deployment) and STYTCH_PROJECT_ID (per-user OAuth, each request resolved to that user's own Google grant). With neither set the transport refuses to start; GTM_MCP_HTTP_ALLOW_UNAUTHENTICATED=true overrides that for local development and binds loopback only.

6. Publish guard: Keep GTM_MCP_ENABLE_PUBLISH=false unless you explicitly intend to publish from an AI client. Publishing incorrect tags to production is the highest-risk operation.

7. Audit logs: The server logs all session events to stderr. Pipe to a logging service in production.

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Development

# Install dependencies
npm install

# TypeScript type check (no emit)
npm run typecheck

# Build
npm run build

# Watch mode
npm run build:watch

# Run dev server (stdio, with hot-reload)
npm run dev

# Run HTTP dev server
npm run dev:http

# Tests (run `npm run build` first — some suites test the compiled dist)
npm test

# Smoke test: server boots and answers tools/list
npm run smoke -- --mcp dist/index.js

# Full-surface smoke test: invokes ALL registered tools with a sanitized,
# credential-free env — every handler must respond cleanly (no crash/hang)
npm run smoke:all

# MCP Inspector (interactive tool debugging)
npm run inspector

Project Structure

samarth-gtm-mcp/
├── src/
│   ├── index.ts              # Entry point — stdio/HTTP transport setup
│   ├── server.ts             # MCP server factory + tool registration
│   ├── auth/
│   │   └── googleAuth.ts     # OAuth2 / service account auth
│   ├── tools/
│   │   ├── index.ts          # Tool registration aggregator
│   │   ├── accounts.ts       # accounts/list, accounts/get
│   │   ├── containers.ts     # containers/list/get/create
│   │   ├── workspaces.ts     # workspaces + sync/resolve_conflict
│   │   ├── tags.ts           # tags CRUD
│   │   ├── triggers.ts       # triggers CRUD
│   │   ├── variables.ts      # variables CRUD
│   │   ├── folders.ts        # folders CRUD + move_entities
│   │   ├── builtInVariables.ts # enable/disable/revert built-ins
│   │   ├── versions.ts       # versions list/get/create/publish/delete
│   │   ├── publish.ts        # quick_preview, versions_publish, create+publish
│   │   ├── audit.ts          # audit_container analytics checks
│   │   ├── export.ts         # export_container JSON dump
│   │   ├── environments.ts   # environments CRUD + reauthorize
│   │   ├── userPermissions.ts # account-level user permissions
│   │   ├── serverSide.ts     # clients, transformations, zones, templates, gtag config
│   │   ├── ga4Admin.ts       # read-only GA4 Admin tools (ga4_*)
│   │   └── ga4Data.ts        # read-only GA4 Data API reporting
│   ├── utils/
│   │   ├── guardrails.ts     # Guardrail enforcement, error formatting
│   │   ├── gtmClient.ts      # googleapis GTM v2 client factory
│   │   ├── ga4Client.ts      # GA4 Admin/Data client factories
│   │   ├── apiRetry.ts       # retry/backoff config (429/5xx, reads only)
│   │   ├── pagination.ts     # transparent nextPageToken following
│   │   ├── schemas.ts        # shared Zod input schemas
│   │   └── toolResponse.ts   # standard tool result shaping
│   ├── types/
│   │   ├── gtm.ts            # GTM API type definitions
│   │   └── index.ts
│   ├── scripts/
│   │   ├── auth-google.ts    # Browser-based OAuth onboarding (`npm run auth:google`)
│   │   └── oauth-setup.ts    # Interactive OAuth token helper (legacy paste-the-code flow)
│   └── __tests__/
│       ├── guardrails.node.test.mjs  # guardrails + buildPath
│       ├── auth.node.test.mjs        # env/auth resolution + token file paths
│       ├── pagination.node.test.mjs  # paginate/buildListResult
│       ├── ga4Admin.node.test.mjs    # GA4 tool registration (tests compiled dist)
│       └── apiRetry.node.test.mjs    # retry/backoff config (tests compiled dist)
├── scripts/
│   ├── smoke-test.mjs        # health probe: portal endpoints + MCP tools/list
│   └── smoke-all-tools.mjs   # invokes all tools with sanitized env
├── .env.example
├── .gitignore
├── package.json
├── tsconfig.json
└── README.md

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Releases

Releases are fully automated via semantic-release and GitHub Actions. Every push to main triggers the release.yml workflow, which:

1. Installs dependencies, type-checks, builds, and runs tests.
2. Inspects commits since the last tag using the Conventional Commits spec.
3. Determines the next semantic version (MAJOR.MINOR.PATCH).
4. Updates CHANGELOG.md and bumps the version in package.json / package-lock.json.
5. Commits those files back to main with chore(release): x.y.z [skip ci] (the [skip ci] marker prevents an infinite release loop).
6. Creates a Git tag (vX.Y.Z) and a GitHub Release with auto-generated notes.

The workflow uses the built-in GITHUB_TOKEN and requires no additional secrets. npm publish is disabled — this package is distributed as a binary via the GitHub repo and releases, not via the npm registry.

Conventional Commit Examples

Commit messages drive the version bump:

Breaking change examples

feat!: drop support for Node.js 18

BREAKING CHANGE: minimum required Node version is now 20.

or:

refactor(auth): rename GOOGLE_REFRESH_TOKEN env var

BREAKING CHANGE: GOOGLE_REFRESH_TOKEN is now GTM_GOOGLE_REFRESH_TOKEN.
Update your .env file accordingly.

Dry run locally

To preview what the next release would look like without publishing:

GITHUB_TOKEN=<a-token-with-no-perms-is-fine-for-dry-run> \
  npx semantic-release --dry-run --no-ci

Manual release skip

To intentionally land a commit without triggering a release, use a non-releasing type (chore:, docs:, etc.) or append [skip ci] to the commit subject.

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Troubleshooting

"The caller does not have permission" (403)

• Your Google account may not have access to this GTM account/container
• Service account not added to GTM — see Service Account Limitations
• Check your OAuth scopes on the consent screen

"invalid_grant" or "Token has been expired or revoked"

• Re-run npm run auth:google to refresh the token file
• Or set GOOGLE_REFRESH_TOKEN directly in .env if you prefer env-managed tokens
• If you're stuck in a loop where Google won't return a refresh_token, revoke prior access at myaccount.google.com/permissions and re-run the auth script

"Write operations are disabled"

• Set GTM_MCP_ENABLE_WRITES=true in your .env
• Restart the server / the desktop app

Stdio server shows no output

• The stdio server intentionally writes nothing to stdout (stdout is the JSON-RPC channel)
• Diagnostic output goes to stderr — check your terminal or Claude Desktop logs

Desktop app: Error: Electron uninstall on npm run dev

• The Electron binary downloaded but never finished extracting - see the reliable re-extract fix in apps/desktop/INSTALL.md

TypeScript errors on googleapis types

• Run npm install to ensure all deps are installed
• The googleapis package ships its own types — no @types/googleapis needed

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TODOs / Known Limitations

• workspace_resolve_conflict: The GTM API's resolve_conflict endpoint accepts a full entity body — the exact request body schema is complex. The current implementation passes through the user-supplied JSON; validate it against the entity type before calling.
• containers_create: The usageContext enum values may differ slightly by GTM region/version. Refer to the GTM API docs for the latest allowed values.
• Single-identity HTTP auth is a shared secret: GTM_MCP_HTTP_AUTH_TOKEN gates /mcp with one bearer token for every client, so it identifies the deployment, not the caller. For per-user identity, set STYTCH_PROJECT_ID to enable multi-user mode — see Security Notes.
• HTTP sessions are in-memory: sessions live in the server process, so horizontal scaling requires sticky sessions. Fine for a single team instance; not yet built for multi-instance load balancing.
• Single OAuth identity per deployment — single-identity mode only: without STYTCH_PROJECT_ID, all requests share one Google identity and therefore one Google API quota pool. Heavy multi-user load through one deployment will exhaust it; retries with backoff soften this but don't remove the quota ceiling. Multi-user mode sidesteps it — each member uses their own Google grant and quota.

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Built by Samarth Analytics — Swapnil Jaykar & Sarthak Mandage