play · Filopastry MCP: Risk & Policy

WHAT IT DOES

What play does on Filopastry

AI agents invoke play to trigger actions in Filopastry. 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 play needs a policy

This tool initiates active execution of music playback through the Strudel.cc live coding environment. While not destructive or financial, it executes external operations that affect the audio system state. The severity is medium rather than high because: (1) the blast radius is localized to audio output, (2) it can be stopped by calling a stop/pause function, and (3) it poses no data loss or system compromise risk.

From the tool's definition "Start playing pattern" indicates the tool triggers real-time audio playback, which executes an external operation (audio synthesis/playback) whose effects depend on the pattern argument and cannot be paused/reversed instantaneously by the tool itself.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

play Rate-limited

play 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": {
    "play": {
      "limits": [
        {
          "counter": "play_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 Filopastry, so you can run agents against it safely.

FAQ

Questions about play

What does the play tool do? +

Start playing pattern. It is categorised as a Execute tool in the Filopastry MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on play? +

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

What risk level is play? +

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

Can I rate-limit play? +

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

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

play is provided by the Filopastry MCP server (youwenshao/filopastry). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.