mypy · Python MCP: Risk & Policy

WHAT IT DOES

What mypy does on Python

AI agents invoke mypy 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 mypy needs a policy

The tool executes the mypy type-checker as an external process. While mypy itself is read-only in terms of file modifications, it executes an external program whose behavior depends on arguments and project configuration. This falls under Execute as it triggers external operations/process execution rather than simply querying data.

From the tool's definition Runs mypy and returns structured type-check diagnostics

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

mypy Rate-limited

mypy 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": {
    "mypy": {
      "limits": [
        {
          "counter": "mypy_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 mypy

What does the mypy tool do? +

Runs mypy and returns structured type-check diagnostics (file, line, severity, message, code). 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 mypy? +

Register the Python MCP server in PolicyLayer and add a rule for mypy: 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 mypy? +

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

Can I rate-limit mypy? +

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

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

mypy 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

mypy 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 →