add_to_suppression_list · Campaign Monitor MCP

WHAT IT DOES

What add_to_suppression_list does on Campaign Monitor MCP

AI agents use add_to_suppression_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 add_to_suppression_list needs a policy

This tool modifies data (adds email addresses to a suppression list) but the operation is reversible—addresses can be removed from the suppression list if needed. It does not delete data irreversibly, execute arbitrary code, or move money.

From the tool's definition Tool name 'add_to_suppression_list' and description 'Add email addresses to a client' indicate modification of suppression list data. This creates or modifies suppression records, which are reversible additions to a blocklist/exclusion list.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_to_suppression_list Rate-limited

add_to_suppression_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": {
    "add_to_suppression_list": {
      "limits": [
        {
          "counter": "add_to_suppression_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 add_to_suppression_list

What does the add_to_suppression_list tool do? +

Add email addresses to a client. 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 add_to_suppression_list? +

Register the Campaign Monitor MCP server in PolicyLayer and add a rule for add_to_suppression_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 add_to_suppression_list? +

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

Can I rate-limit add_to_suppression_list? +

Yes. Add a rate_limit block to the add_to_suppression_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 add_to_suppression_list completely? +

Set action: deny in the PolicyLayer policy for add_to_suppression_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 add_to_suppression_list? +

add_to_suppression_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.