set_stream_favorite · Packmate MCP: Risk & Policy

WHAT IT DOES

What set_stream_favorite does on Packmate

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

WHY IT NEEDS A POLICY

Why set_stream_favorite needs a policy

This tool creates or modifies metadata (favorite flag) on a stream in a reversible manner. It is a Write operation because it alters state but does not delete data, execute code, move funds, or trigger external processes. The blast radius is minimal—a misused agent could only toggle favorite flags. Severity is low because the operation is fully reversible and has no destructive, financial, or execution implications.

From the tool's definition Tool description states 'Mark or unmark a stream as favorite' — a reversible state modification operation that changes metadata without affecting underlying data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_stream_favorite Rate-limited

set_stream_favorite 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_stream_favorite": {
      "limits": [
        {
          "counter": "set_stream_favorite_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 Packmate, so you can run agents against it safely.

FAQ

Questions about set_stream_favorite

What does the set_stream_favorite tool do? +

Mark or unmark a stream as favorite. It is categorised as a Write tool in the Packmate 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_stream_favorite? +

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

What risk level is set_stream_favorite? +

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

Can I rate-limit set_stream_favorite? +

Yes. Add a rate_limit block to the set_stream_favorite 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_stream_favorite completely? +

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

set_stream_favorite is provided by the Packmate MCP server (umbra2728/packmate-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.