AI agents use midi_sort 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.
Sorting MIDI events reorders data in a reversible manner without permanent deletion or destruction of content. The operation modifies the sequence/arrangement of existing MIDI events but does not delete, execute external code, or trigger irreversible changes. This is a write operation with minimal blast radius—worst case is the user must undo or manually restore the original event order.
From the tool's definition Tool name 'midi_sort' and description 'Sort MIDI events by time' indicates modification of MIDI event ordering within a project.
Documented attack patterns abuse exactly the kind of access midi_sort 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_sort:
{
"version": "1",
"default": "deny",
"tools": {
"midi_sort": {
"limits": [
{
"counter": "midi_sort_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}midi_sort 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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Sort MIDI events by time. 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_sort: 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_sort 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_sort 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_sort. 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_sort 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.