custom_merge_leads · Marketo MCP Server MCP: Risk & Policy

WHAT IT DOES

What custom_merge_leads does on Marketo MCP Server

AI agents use custom_merge_leads 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_merge_leads needs a policy

Merging leads modifies existing data records (combining two lead entities into one), which is a Write action rather than Destructive since the data itself is retained, not irreversibly deleted. However, it affects critical CRM data (lead records), giving it high severity due to potential impact on marketing automation workflows and customer data integrity.

From the tool's definition Tool description states it 'Calls the Marketo REST API directly' for a 'custom_merge_leads' operation. 'Merge' indicates combining/modifying lead records, which is a reversible write operation on customer data in a CRM system.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

custom_merge_leads Rate-limited

custom_merge_leads 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_merge_leads": {
      "limits": [
        {
          "counter": "custom_merge_leads_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_merge_leads

What does the custom_merge_leads 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_merge_leads? +

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

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

Can I rate-limit custom_merge_leads? +

Yes. Add a rate_limit block to the custom_merge_leads 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_merge_leads completely? +

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

custom_merge_leads 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.