send_note_on · Midi MCP: Risk & Policy

WHAT IT DOES

What send_note_on does on Midi

AI agents invoke send_note_on to trigger actions in Midi. 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 send_note_on needs a policy

This tool sends a MIDI Note On message to external hardware instruments, causing them to produce sound. It executes an external operation whose effect depends on arguments (channel, note, velocity). While the effect is transient and reversible (note can be stopped), it constitutes triggering an external action rather than merely reading or writing data.

From the tool's definition 'Send a MIDI Note On message' — triggers an external operation on hardware MIDI devices (synths, drum machines)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

send_note_on Rate-limited

send_note_on 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": {
    "send_note_on": {
      "limits": [
        {
          "counter": "send_note_on_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 Midi, so you can run agents against it safely.

FAQ

Questions about send_note_on

What does the send_note_on tool do? +

Send a MIDI Note On message. It is categorised as a Execute tool in the Midi MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on send_note_on? +

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

What risk level is send_note_on? +

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

Can I rate-limit send_note_on? +

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

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

send_note_on is provided by the Midi MCP server (pnilan/midi-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

// THE FULL RECORD

send_note_on is one line of Midi's registry record.

The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.

Teams ship this data inside their own products. See what a licence covers →