play_by_index · Music MCP: Risk & Policy

WHAT IT DOES

What play_by_index does on Music

AI agents invoke play_by_index to trigger actions in Music. 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 play_by_index needs a policy

This tool initiates music playback by triggering an external operation (playing audio), which constitutes an Execute action. It causes a side effect in an external system (music player) rather than simply reading or writing data. Severity is medium as misuse could cause unwanted audio playback but has limited broader impact.

From the tool's definition 播放最近搜索结果中的第几首歌 (Play the nth song from recent search results) — triggers external playback operation

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

play_by_index Rate-limited

play_by_index 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": {
    "play_by_index": {
      "limits": [
        {
          "counter": "play_by_index_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 Music, so you can run agents against it safely.

FAQ

Questions about play_by_index

What does the play_by_index tool do? +

播放最近搜索结果中的第几首歌（从 1 开始）. It is categorised as a Execute tool in the Music MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on play_by_index? +

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

What risk level is play_by_index? +

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

Can I rate-limit play_by_index? +

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

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

play_by_index is provided by the Music MCP server (jxiufen/music-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.