play_rtttl · Ulanzi MCP: Risk & Policy

WHAT IT DOES

What play_rtttl does on Ulanzi

AI agents invoke play_rtttl to trigger actions in Ulanzi. 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_rtttl needs a policy

This tool triggers an external operation on a physical device (Ulanzi TC001 pixel clock) — playing audio/melody. It executes an action on the device with real-world effects. It's not purely data retrieval (Read) nor does it modify stored data (Write). It fits Execute as it triggers an external operation whose effects depend on the melody string argument.

From the tool's definition Play a RTTTL melody string directly

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

play_rtttl Rate-limited

play_rtttl 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_rtttl": {
      "limits": [
        {
          "counter": "play_rtttl_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 Ulanzi, so you can run agents against it safely.

FAQ

Questions about play_rtttl

What does the play_rtttl tool do? +

Play a RTTTL melody string directly. It is categorised as a Execute tool in the Ulanzi 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_rtttl? +

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

What risk level is play_rtttl? +

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

Can I rate-limit play_rtttl? +

Yes. Add a rate_limit block to the play_rtttl 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_rtttl completely? +

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

play_rtttl is provided by the Ulanzi MCP server (jelloeater/ulanzi-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.