run_code · Melo MCP: Risk & Policy

WHAT IT DOES

What run_code does on Melo

AI agents invoke run_code to trigger actions in Melo. 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 run_code needs a policy

This tool directly executes code in a game development environment (Roblox Studio), allowing an AI agent to run arbitrary Luau scripts that could modify game state, access sensitive data, manipulate instances, or trigger unintended side effects. While not inherently destructive by itself, the Execute category is appropriate because the effects depend entirely on the code argument provided.

From the tool's definition Tool executes arbitrary Luau code in Roblox Studio with "Execute Luau" functionality and returns printed output. Accepts code as a string argument with no apparent restrictions on what can be executed.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

run_code Rate-limited

run_code 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": {
    "run_code": {
      "limits": [
        {
          "counter": "run_code_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 Melo, so you can run agents against it safely.

FAQ

Questions about run_code

What does the run_code tool do? +

Execute Luau code in Studio and return printed output. Alias for execute_luau. Args: - code (string): Luau code to execute Returns: Captured print output. It is categorised as a Execute tool in the Melo MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on run_code? +

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

What risk level is run_code? +

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

Can I rate-limit run_code? +

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

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

run_code is provided by the Melo MCP server (yannyhl/linkedsword-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.