Set the edit cursor position.
AI agents use set_cursor_position 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.
This tool modifies cursor position state in the DAW, which is a reversible change with no permanent data loss. It does not execute arbitrary code, delete content, or cause financial effects. While it changes application state, the impact is confined to UI/playback position—easily undoable and low risk.
From the tool's definition Tool name 'set_cursor_position' and description 'Set the edit cursor position' indicate modification of the playback/edit position state in REAPER DAW.
Documented attack patterns abuse exactly the kind of access set_cursor_position 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 set_cursor_position:
{
"version": "1",
"default": "deny",
"tools": {
"set_cursor_position": {
"limits": [
{
"counter": "set_cursor_position_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_cursor_position 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 the edit cursor position. 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 set_cursor_position: 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.
set_cursor_position 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 set_cursor_position 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 set_cursor_position. 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.
set_cursor_position 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.