AI agents use midi_set_note to create or update resources in ReaperMCP — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your ReaperMCP environment.
The tool modifies MIDI note data (a write operation) within a music production session. While the description is empty, the tool name and server context make the intent clear. Severity is medium because: (1) changes are reversible in a DAW undo-stack, (2) impact is scoped to a single note/project, and (3) no destructive deletion or financial harm occurs.
From the tool's definition Tool name 'midi_set_note' indicates modification of MIDI note data. Context: sibling tools include 'create_chord_progression', 'create_drum_pattern', and other music production actions.
Documented attack patterns abuse exactly the kind of access midi_set_note gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and ReaperMCP, and nothing reaches the server without passing your rules. This is the rule we recommend for midi_set_note:
{
"version": "1",
"default": "deny",
"tools": {
"midi_set_note": {
"limits": [
{
"counter": "midi_set_note_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}midi_set_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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midi_set_note. It is categorised as a Write tool in the ReaperMCP 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 midi_set_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 ReaperMCP. Nothing to install.
midi_set_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 midi_set_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 midi_set_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.
midi_set_note is provided by the Reaper MCP server (xdarkzx/reaper-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from ReaperMCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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138 ReaperMCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.