set_tempo · Orpheus MCP: Risk & Policy

WHAT IT DOES

What set_tempo does on Orpheus

AI agents use set_tempo 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_tempo needs a policy

set_tempo creates or modifies project data (tempo setting) reversibly without deleting or executing arbitrary code. While it affects how audio plays back, the change itself is not destructive and can be undone. This is a classic Write category action. Severity is medium because tempo changes could subtly alter the character of a mix or project workflow, but the impact is localized and reversible.

From the tool's definition Tool modifies project state by setting tempo in BPM; operation is reversible via undo or setting a different tempo value. Description explicitly states 'Set the project tempo', a write operation on project configuration.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_tempo Rate-limited

set_tempo 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_tempo": {
      "limits": [
        {
          "counter": "set_tempo_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_tempo

What does the set_tempo tool do? +

Set the project tempo in BPM (downstream: seconds_per_beat = 60 / bpm). 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_tempo? +

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

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

Can I rate-limit set_tempo? +

Yes. Add a rate_limit block to the set_tempo 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_tempo completely? +

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

set_tempo 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.