create_external_session · Campaign Monitor MCP

WHAT IT DOES

What create_external_session does on Campaign Monitor MCP

AI agents invoke create_external_session to trigger actions in Campaign Monitor MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why create_external_session needs a policy

Creating an authenticated session is an external operation that grants access and has security implications beyond simple data creation. It triggers authentication/authorization flows in an external system, making it an Execute-category action. Misuse could allow unauthorized embedding or session hijacking, hence medium severity.

From the tool's definition Initiate a new login session for embedding Campaign Monitor in an iframe

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_external_session Rate-limited

create_external_session stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "create_external_session": {
      "limits": [
        {
          "counter": "create_external_session_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-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 create_external_session

What does the create_external_session tool do? +

Initiate a new login session for embedding Campaign Monitor in an iframe. It is categorised as a Execute tool in the Campaign Monitor MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on create_external_session? +

Register the Campaign Monitor MCP server in PolicyLayer and add a rule for create_external_session: 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 create_external_session? +

create_external_session is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit create_external_session? +

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

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

create_external_session 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.