stop_playtest · Melo MCP: Risk & Policy

WHAT IT DOES

What stop_playtest does on Melo

AI agents invoke stop_playtest 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 stop_playtest needs a policy

This tool executes a command to terminate the current playtest session in Roblox Studio, affecting the runtime state of the development environment. Though reversible (another playtest can be started), it is an active control operation that interrupts execution and returns captured telemetry, placing it in Execute rather than Write.

From the tool's definition The tool description states it will 'End the current play session' which terminates an active process/operation. The return of 'output logs' indicates it captures side effects of execution.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

stop_playtest Rate-limited

stop_playtest 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": {
    "stop_playtest": {
      "limits": [
        {
          "counter": "stop_playtest_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 stop_playtest

What does the stop_playtest tool do? +

End the current play session and return all captured output logs. Returns: { output: string, errors: string[], duration: number }. 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 stop_playtest? +

Register the Melo MCP server in PolicyLayer and add a rule for stop_playtest: 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 stop_playtest? +

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

Can I rate-limit stop_playtest? +

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

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

stop_playtest 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.