update_list · Campaign Monitor MCP: Risk & Policy

WHAT IT DOES

What update_list does on Campaign Monitor MCP

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

WHY IT NEEDS A POLICY

Why update_list needs a policy

This tool modifies subscriber list configuration/settings but does not delete data, execute code, or commit financial transactions. It is a classic Write operation that can be undone by updating settings again. Severity is medium because misconfiguration of lists could impact email campaign behavior and subscriber experience, but the impact is containable and reversible.

From the tool's definition Tool name 'update_list' and description 'Update settings for a subscriber list' indicate modification of existing data. The action is reversible (settings can be changed again), not destructive or financial.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_list Rate-limited

update_list 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": {
    "update_list": {
      "limits": [
        {
          "counter": "update_list_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 Campaign Monitor MCP, so you can run agents against it safely.

FAQ

Questions about update_list

What does the update_list tool do? +

Update settings for a subscriber list. It is categorised as a Write tool in the Campaign Monitor MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_list? +

Register the Campaign Monitor MCP server in PolicyLayer and add a rule for update_list: 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 Campaign Monitor MCP. Nothing to install.

What risk level is update_list? +

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

Can I rate-limit update_list? +

Yes. Add a rate_limit block to the update_list 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 update_list completely? +

Set action: deny in the PolicyLayer policy for update_list. 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 update_list? +

update_list is provided by the Campaign Monitor MCP server (pauliowest/cmon-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.