AI agents use set_item_length to create or update resources in Reaper Reapy — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Reaper Reapy environment.
This tool modifies existing data (item length) reversibly—the change can be undone in REAPER and the length can be set again. It does not execute arbitrary code, delete data, or cause financial impact. It is a Write operation. Severity is medium because misuse could corrupt a user's audio project by setting incorrect lengths, but changes are reversible.
From the tool's definition Tool name 'set_item_length' suggests modifying the duration/length property of an audio item in REAPER DAW. No description provided, but context from sibling tools (add_fx, create_track, create_midi_item, etc.) confirms this is a REAPER editing operation.
Documented attack patterns abuse exactly the kind of access set_item_length gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Reaper Reapy, and nothing reaches the server without passing your rules. This is the rule we recommend for set_item_length:
{
"version": "1",
"default": "deny",
"tools": {
"set_item_length": {
"limits": [
{
"counter": "set_item_length_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_item_length 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_item_length. It is categorised as a Write tool in the Reaper Reapy MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Reaper Reapy MCP server in PolicyLayer and add a rule for set_item_length: 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 Reapy. Nothing to install.
set_item_length 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_item_length 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_item_length. 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_item_length is provided by the Reaper Reapy MCP server (wegitor/reaper-reapy-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 47 Reaper Reapy tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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47 Reaper Reapy tools catalogued and risk-classified — across an index of 42,500+ MCP servers.