fl_eval · Flemcee MCP: Risk & Policy

WHAT IT DOES

What fl_eval does on Flemcee

AI agents invoke fl_eval to trigger actions in Flemcee. 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 fl_eval needs a policy

This tool runs arbitrary Python expressions inside FL Studio, which constitutes code execution. A malicious or mistaken expression could manipulate FL Studio state, access the filesystem, or cause unintended side effects. The blast radius is high since Python execution inside a DAW environment is largely unrestricted.

From the tool's definition 'Evaluate a Python expression inside FL Studio and return the result' — executes arbitrary Python code within FL Studio environment

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

fl_eval Rate-limited

fl_eval 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": {
    "fl_eval": {
      "limits": [
        {
          "counter": "fl_eval_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 Flemcee, so you can run agents against it safely.

FAQ

Questions about fl_eval

What does the fl_eval tool do? +

Evaluate a Python expression inside FL Studio and return the result. It is categorised as a Execute tool in the Flemcee MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on fl_eval? +

Register the Flemcee MCP server in PolicyLayer and add a rule for fl_eval: 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 Flemcee. Nothing to install.

What risk level is fl_eval? +

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

Can I rate-limit fl_eval? +

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

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

fl_eval is provided by the Flemcee MCP server (tylerjharden/flemcee). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.