create_list · DataMerge MCP: Risk & Policy

WHAT IT DOES

What create_list does on DataMerge MCP

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

WHY IT NEEDS A POLICY

Why create_list needs a policy

The POST HTTP method on a /lists endpoint creates a new data structure (a list) in the DataMerge system. This is a reversible write operation—lists can be deleted or modified without permanent data loss. It does not execute arbitrary code, delete data, or move money.

From the tool's definition Tool description explicitly states 'POST /v1/lists' with parameters for name and object_type, indicating HTTP POST request that creates a new list resource.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_list Rate-limited

create_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": {
    "create_list": {
      "limits": [
        {
          "counter": "create_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 DataMerge MCP, so you can run agents against it safely.

FAQ

Questions about create_list

What does the create_list tool do? +

POST /v1/lists. Body: name, object_type (company or contact). It is categorised as a Write tool in the DataMerge 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 create_list? +

Register the DataMerge MCP server in PolicyLayer and add a rule for create_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 DataMerge MCP. Nothing to install.

What risk level is create_list? +

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

Can I rate-limit create_list? +

Yes. Add a rate_limit block to the create_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 create_list completely? +

Set action: deny in the PolicyLayer policy for create_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 create_list? +

create_list is provided by the DataMerge MCP server (poolside-ventures/datamerge-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.