stop · Scythe MCP REAPER MCP: Risk & Policy

WHAT IT DOES

What stop does on Scythe MCP REAPER

AI agents invoke stop to trigger actions in Scythe MCP REAPER. 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 needs a policy

While stopping playback is a benign action with no data destruction or financial impact, it is fundamentally an Execute operation—it triggers a state change in an external system (REAPER) based on the tool invocation. It is not a Read (no data retrieval), Write (no data creation/modification), Destructive (no irreversible loss), or Financial operation.

From the tool's definition Tool is named 'stop' and described as 'Stop playback.' within a REAPER DAW control server that supports 'transport control' operations. Playback control via OSC/ReaScript integration constitutes triggering an external operation (the DAW).

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

stop Rate-limited

stop 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": {
      "limits": [
        {
          "counter": "stop_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 Scythe MCP REAPER, so you can run agents against it safely.

FAQ

Questions about stop

What does the stop tool do? +

Stop playback. It is categorised as a Execute tool in the Scythe MCP REAPER 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? +

Register the Scythe MCP REAPER MCP server in PolicyLayer and add a rule for stop: 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 Scythe MCP REAPER. Nothing to install.

What risk level is stop? +

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

Can I rate-limit stop? +

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

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

stop is provided by the Scythe MCP REAPER MCP server (yura9011/scythe_mcp_reaper). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.