set_fx_param · Orpheus MCP: Risk & Policy

WHAT IT DOES

What set_fx_param does on Orpheus

AI agents use set_fx_param 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 set_fx_param needs a policy

This tool writes/modifies a parameter on an audio effect in a REAPER project. It changes project state but is reversible (parameters can be reset). It does not delete data, execute arbitrary code, or involve finances. Severity is medium because misuse could alter audio processing settings across a project, but the effect is non-destructive and recoverable.

From the tool's definition 'Set an FX parameter' — modifies an FX parameter value in the project using name-to-index resolution

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_fx_param Rate-limited

set_fx_param 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": {
    "set_fx_param": {
      "limits": [
        {
          "counter": "set_fx_param_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 set_fx_param

What does the set_fx_param tool do? +

Set an FX parameter with name→index resolution (so 'ratio' works, not just index 7). 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 set_fx_param? +

Register the Orpheus MCP server in PolicyLayer and add a rule for set_fx_param: 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 set_fx_param? +

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

Can I rate-limit set_fx_param? +

Yes. Add a rate_limit block to the set_fx_param 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 set_fx_param completely? +

Set action: deny in the PolicyLayer policy for set_fx_param. 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 set_fx_param? +

set_fx_param 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.