AI agents use add_midi_note to create or update resources in Reaper — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Reaper environment.
The tool creates new MIDI note data in REAPER DAW, which is a reversible modification (notes can be deleted/edited). This is a Write operation rather than Read (retrieves data) or Destructive (permanently deletes). Severity is medium because misuse could corrupt a music project, but changes are reversible.
From the tool's definition Tool name is 'add_midi_note' which indicates creating/adding MIDI data. Sibling tools like 'add_midi_notes_batch', 'add_compressor', 'add_eq', and 'add_envelope_point' all perform Write operations (creating or modifying DAW state).
Documented attack patterns abuse exactly the kind of access add_midi_note gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Reaper, and nothing reaches the server without passing your rules. This is the rule we recommend for add_midi_note:
{
"version": "1",
"default": "deny",
"tools": {
"add_midi_note": {
"limits": [
{
"counter": "add_midi_note_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}add_midi_note stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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add_midi_note. It is categorised as a Write tool in the Reaper MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Reaper MCP server in PolicyLayer and add a rule for add_midi_note: 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 Reaper. Nothing to install.
add_midi_note is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the add_midi_note 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.
Set action: deny in the PolicyLayer policy for add_midi_note. 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.
add_midi_note is provided by the Reaper MCP server (twelvetake-studios/reaper-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Reaper, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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158 Reaper tools catalogued and risk-classified — across an index of 43,000+ MCP servers.