custom_update_email_headers · Marketo MCP Server MCP

WHAT IT DOES

What custom_update_email_headers does on Marketo MCP Server

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

WHY IT NEEDS A POLICY

Why custom_update_email_headers needs a policy

Updating email headers is a reversible write operation that modifies email configuration in Marketo. While headers can affect email delivery and appearance, this is not destructive (reversible), not financial, and not arbitrary code execution. The 'custom' prefix and direct API call suggest some flexibility in implementation, but the primary function remains data modification.

From the tool's definition Tool name 'custom_update_email_headers' indicates modification of email headers; description states it 'Calls the Marketo REST API directly' for email management operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

custom_update_email_headers Rate-limited

custom_update_email_headers 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": {
    "custom_update_email_headers": {
      "limits": [
        {
          "counter": "custom_update_email_headers_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 Marketo MCP Server, so you can run agents against it safely.

FAQ

Questions about custom_update_email_headers

What does the custom_update_email_headers tool do? +

[CUSTOM] Calls the Marketo REST API directly (not Adobe's native MCP). It is categorised as a Write tool in the Marketo MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on custom_update_email_headers? +

Register the Marketo MCP Server MCP server in PolicyLayer and add a rule for custom_update_email_headers: 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 Marketo MCP Server. Nothing to install.

What risk level is custom_update_email_headers? +

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

Can I rate-limit custom_update_email_headers? +

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

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

custom_update_email_headers is provided by the Marketo MCP Server MCP server (tyron-pretorius/marketo-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.