constrain_to_key · Orpheus MCP: Risk & Policy

WHAT IT DOES

What constrain_to_key does on Orpheus

AI agents use constrain_to_key to create or update resources in Orpheus — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Orpheus environment.

WHY IT NEEDS A POLICY

Why constrain_to_key needs a policy

This tool transforms audio/MIDI data (notes) in a reversible way—pitches are adjusted but can be undone, which is characteristic of a Write operation. It is not Destructive because the original note information is not irreversibly deleted, only modified.

From the tool's definition The tool modifies note data by 'snap[ping]' pitches to in-key values, and the description explicitly states 'before writing', indicating the tool commits changes to the REAPER project.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

constrain_to_key Rate-limited

constrain_to_key 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "constrain_to_key": {
      "limits": [
        {
          "counter": "constrain_to_key_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Orpheus, so you can run agents against it safely.

FAQ

Questions about constrain_to_key

What does the constrain_to_key tool do? +

Snap a proposed note set to the nearest in-key pitches before writing. It is categorised as a Write tool in the Orpheus MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on constrain_to_key? +

Register the Orpheus MCP server in PolicyLayer and add a rule for constrain_to_key: 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 Orpheus. Nothing to install.

What risk level is constrain_to_key? +

constrain_to_key is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit constrain_to_key? +

Yes. Add a rate_limit block to the constrain_to_key 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.

How do I block constrain_to_key completely? +

Set action: deny in the PolicyLayer policy for constrain_to_key. 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.

What MCP server provides constrain_to_key? +

constrain_to_key is provided by the Orpheus MCP server (mal0ware/orpheus). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.