Set loop points.
AI agents use selection_set_loop 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.
Setting loop points modifies REAPER's playback configuration reversibly. While not destructive, this falls under Write because it creates or modifies session state. Severity is medium: misuse could disrupt a user's workflow or session organization, but changes are easily undone via undo or re-adjustment. Confidence is 0.85 due to the straightforward nature of the function; minimal ambiguity.
From the tool's definition Tool name 'selection_set_loop' and description 'Set loop points' indicate modifying loop configuration in REAPER. This is a reversible state change to playback parameters, not data deletion or code execution.
Documented attack patterns abuse exactly the kind of access selection_set_loop 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 selection_set_loop:
{
"version": "1",
"default": "deny",
"tools": {
"selection_set_loop": {
"limits": [
{
"counter": "selection_set_loop_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}selection_set_loop 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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Set loop points. 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 selection_set_loop: 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.
selection_set_loop 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 selection_set_loop 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 selection_set_loop. 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.
selection_set_loop 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.