black · Python MCP: Risk & Policy

WHAT IT DOES

What black does on Python

AI agents invoke black to trigger actions in Python. 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 black needs a policy

This tool executes an external code formatting process (Black) that modifies source files on disk. It is not a pure read — it can reformat (overwrite) files. Since formatting is reversible via version control, it doesn't rise to Destructive, but it does run an external tool that causes side effects (file modifications), placing it in Execute.

From the tool's definition Runs Black code formatter and returns structured results (files changed, unchanged, would reformat)

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

black Rate-limited

black 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": {
    "black": {
      "limits": [
        {
          "counter": "black_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 Python, so you can run agents against it safely.

FAQ

Questions about black

What does the black tool do? +

Runs Black code formatter and returns structured results (files changed, unchanged, would reformat). It is categorised as a Execute tool in the Python MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on black? +

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

What risk level is black? +

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

Can I rate-limit black? +

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

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

black is provided by the Python MCP server (Dave-London/Pare). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

// THE FULL RECORD

black is one line of Python's registry record.

The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.

Teams ship this data inside their own products. See what a licence covers →