AI agents use select_all_tracks 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.
Selecting all tracks modifies the selection state in REAPER, which is a reversible state change. It does not read data, execute code, or destroy anything, but it does alter the application state (track selection) which can have downstream effects if subsequent operations act on the selection.
From the tool's definition Select all tracks
Documented attack patterns abuse exactly the kind of access select_all_tracks 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 select_all_tracks:
{
"version": "1",
"default": "deny",
"tools": {
"select_all_tracks": {
"limits": [
{
"counter": "select_all_tracks_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}select_all_tracks 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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Select all tracks. 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 select_all_tracks: 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.
select_all_tracks 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 select_all_tracks 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 select_all_tracks. 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.
select_all_tracks 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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