gtm_create_variable · Gtm MCP: Risk & Policy

WHAT IT DOES

What gtm_create_variable does on Gtm

AI agents use gtm_create_variable to create or update resources in Gtm — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Gtm environment.

WHY IT NEEDS A POLICY

Why gtm_create_variable needs a policy

This tool creates a new variable within Google Tag Manager, which is a reversible write operation. Variables are configuration objects used in tracking and tag management. While creation is reversible (variables can be deleted), misuse could inject malicious tracking logic or compromise GTM configurations with medium blast radius.

From the tool's definition Tool name 'gtm_create_variable' and description 'Create a new variable in a GTM container' explicitly state creation of a new data object. The server description confirms this tool enables 'creation, update, and publishing' of GTM resources.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

gtm_create_variable Rate-limited

gtm_create_variable stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "gtm_create_variable": {
      "limits": [
        {
          "counter": "gtm_create_variable_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Gtm, so you can run agents against it safely.

FAQ

Questions about gtm_create_variable

What does the gtm_create_variable tool do? +

Create a new variable in a GTM container. It is categorised as a Write tool in the Gtm MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on gtm_create_variable? +

Register the Gtm MCP server in PolicyLayer and add a rule for gtm_create_variable: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Gtm. Nothing to install.

What risk level is gtm_create_variable? +

gtm_create_variable is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit gtm_create_variable? +

Yes. Add a rate_limit block to the gtm_create_variable rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block gtm_create_variable completely? +

Set action: deny in the PolicyLayer policy for gtm_create_variable. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides gtm_create_variable? +

gtm_create_variable is provided by the Gtm MCP server (tijevlam/gtm-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.