upsert_song · Bandmate MCP Server MCP: Risk & Policy

WHAT IT DOES

What upsert_song does on Bandmate MCP Server

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

WHY IT NEEDS A POLICY

Why upsert_song needs a policy

This tool performs Write operations: it creates new songs or updates existing ones. Both operations are reversible (songs can be deleted or modified again), so it does not qualify as Destructive. The severity is medium because misuse by an AI agent could create or modify many songs in a user's music library, causing data clutter or incorrect metadata, but this would not cause permanent loss or financial impact.

From the tool's definition Tool description states 'Create a new song or update an existing one', which explicitly indicates reversible create and modify operations.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

upsert_song Rate-limited

upsert_song 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": {
    "upsert_song": {
      "limits": [
        {
          "counter": "upsert_song_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 Bandmate MCP Server, so you can run agents against it safely.

FAQ

Questions about upsert_song

What does the upsert_song tool do? +

Create a new song or update an existing one. If id is provided, updates that song; otherwise creates a new one. It is categorised as a Write tool in the Bandmate MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on upsert_song? +

Register the Bandmate MCP Server MCP server in PolicyLayer and add a rule for upsert_song: 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 Bandmate MCP Server. Nothing to install.

What risk level is upsert_song? +

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

Can I rate-limit upsert_song? +

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

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

upsert_song is provided by the Bandmate MCP Server MCP server (jnicolasgomez/bandmate-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.