custom_add_custom_object_type_fields

WHAT IT DOES

What custom_add_custom_object_type_fields does on Marketo MCP Server

AI agents use custom_add_custom_object_type_fields 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_add_custom_object_type_fields needs a policy

Adding custom object type fields modifies the data structure/schema of a Marketo instance, which is a Write operation (reversible via deletion/modification). Severity is high because misconfigured custom fields could affect data integrity, reporting, and lead management workflows across the platform.

From the tool's definition Tool name includes 'add' and 'custom_object_type_fields', indicating creation/modification of schema or data structures. Description states it 'Calls the Marketo REST API directly', confirming it performs API operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

custom_add_custom_object_type_fields Rate-limited

custom_add_custom_object_type_fields 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_add_custom_object_type_fields": {
      "limits": [
        {
          "counter": "custom_add_custom_object_type_fields_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_add_custom_object_type_fields

What does the custom_add_custom_object_type_fields 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_add_custom_object_type_fields? +

Register the Marketo MCP Server MCP server in PolicyLayer and add a rule for custom_add_custom_object_type_fields: 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_add_custom_object_type_fields? +

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

Can I rate-limit custom_add_custom_object_type_fields? +

Yes. Add a rate_limit block to the custom_add_custom_object_type_fields 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_add_custom_object_type_fields completely? +

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

custom_add_custom_object_type_fields 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.