Google Tag Manager MCP Server (Alpha)

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This repo contains the source code for running a local MCP server that interacts with APIs for Google Tag Manager.

Features

• No frequent authentication. Standard Google ADC with your own OAuth client is all you need. Everything runs on your machine, straight against the GTM API.
• No service account required. The server runs as you, with the GTM permissions your account already has.
• Built for LLM context windows. A single GTM tag can be hundreds of lines of JSON; list_* tools return slim skeletons and get_* fetches full detail only when asked.

Tools

The server uses the Google Tag Manager API to provide Tools for use with LLMs. The most frequently used tools are:

Triggers and variables have the same four tools as tags, and versioning and publishing have their own. See Appendix I for the full list.

The write safety model:

• Editing and going live are separate. Create/update/delete only touch the workspace draft; only publish_version changes the live site.
• Updates are merge patches. The model sends just the fields it changes, and the server submits the entity's fingerprint, so a concurrent edit fails cleanly instead of being clobbered.
• Deletes and publishing need confirm=true, and every destructive tool is declared with destructiveHint.
• No blind retries on writes. Rate-limit rejections are retried, ambiguous 5xx errors are not, so a create is never silently duplicated.

Prerequisites

• Python >= 3.10
• pipx
• The gcloud CLI
• A Google account with access to your GTM containers
• A GCP project (used only for quota attribution)

Setup instructions

1. Install

pipx install tagmanager-mcp

2. Enable the Tag Manager API on your quota project

gcloud services enable tagmanager.googleapis.com --project=YOUR_PROJECT

3. Create a Desktop OAuth client

Check out Manage OAuth Clients for how to create an OAuth client. Two choices matter here: pick application type Desktop app, and publish the app to Production, because an app left in Testing issues refresh tokens that expire after 7 days. Download the client JSON at the end — step 4 needs it.

Why your own client? Google may block gcloud's built-in one for Tag Manager scopes ("This app is blocked"), and that block is not something you can work around from your side.

4. Log in

gcloud auth application-default login \
  --client-id-file=path/to/your-client.json \
  --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.publish,\
https://www.googleapis.com/auth/cloud-platform

gcloud auth application-default set-quota-project YOUR_PROJECT

The browser will warn "Google hasn't verified this app" — it is your own app; choose Advanced → Continue.

Those scopes unlock everything. Drop the lines you do not want:

Tools outside your granted scopes fail with a clear re-login hint, and everything else keeps working.

Connect an MCP client

Configure Claude Code

claude mcp add --scope user tagmanager-mcp -- tagmanager-mcp

--scope user registers the server for every project instead of just the current directory. Verify with claude mcp list, or run /mcp inside a session.

Configure Claude Desktop

Claude Desktop needs the absolute path to the executable. Print it:

which tagmanager-mcp

Open Settings → Developer → Edit Config, which reveals claude_desktop_config.json (~/Library/Application Support/Claude/ on macOS, %APPDATA%\Claude\ on Windows), and add the server with the path you just printed:

{
  "mcpServers": {
    "tagmanager-mcp": {
      "command": "/Users/you/.local/bin/tagmanager-mcp"
    }
  }
}

Save the file and restart Claude Desktop — it reads the config only at startup. The tools then appear under the tools icon in the chat box.

Example prompts

• "Which GTM accounts and containers do I have?"
• "How many tags are in container GTM-XXXXXXX, grouped by type?"
• "Show me the purchase tag's config and which triggers fire it."
• "Does the current workspace have unpublished changes?"
• "Pause every tag that fires on the checkout trigger."
• "Create a custom-event trigger for sign_up and a GA4 event tag that fires on it."

Note on quota

The GTM API allows 10,000 requests/day and 25 requests per 100 seconds per GCP project; per-user overrides do not raise it. Ordinary audit conversations fit comfortably — just avoid sweeping every tag across many containers at once.

Appendix I: A Full List of Tools

Read

Write