kef_previous · Kef MCP: Risk & Policy

WHAT IT DOES

What kef_previous does on Kef

AI agents invoke kef_previous to trigger actions in Kef. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why kef_previous needs a policy

This tool triggers an external operation on a physical device (KEF speaker) to change the currently playing track. It executes a playback control command with side effects on the device state, making it Execute category. The blast radius is low as it only affects media playback.

From the tool's definition Go to the previous track on the KEF

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

kef_previous Rate-limited

kef_previous stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "kef_previous": {
      "limits": [
        {
          "counter": "kef_previous_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about kef_previous

What does the kef_previous tool do? +

Go to the previous track on the KEF. It is categorised as a Execute tool in the Kef MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on kef_previous? +

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

What risk level is kef_previous? +

kef_previous is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit kef_previous? +

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

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

kef_previous is provided by the Kef MCP server (nqrwhal/kef-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.