ruff-format

THE RISK

High Risk

Why ruff-format needs a policy

The tool runs an external formatting command (ruff format) that rewrites source files. This is an Execute action with Write side effects. Since it modifies files but is generally reversible via version control, severity is medium rather than high.

From the tool's definition 'Runs ruff format' — actively executes the ruff formatter tool, modifying files in place

Documented attack patterns abuse exactly the kind of access ruff-format gives an agent:

POLICY

How to control ruff-format

PolicyLayer is an MCP gateway — it sits between your AI agents and Lint, and nothing reaches the server without passing your rules. This is the rule we recommend for ruff-format:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "ruff-format": {
      "limits": [
        {
          "counter": "ruff-format_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

ruff-format 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.

Create a free account and register Lint — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

Govern code and CI agents → Branch allowlists, approval on merges, and rate caps on the build and pipeline tools agents trigger.
High-risk tools in Lint → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about ruff-format

What does the ruff-format tool do? +

Runs ruff format and returns structured results (files changed, file list). It is categorised as a Execute tool in the Lint MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on ruff-format? +

Register the Lint MCP server in PolicyLayer and add a rule for ruff-format: 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 Lint. Nothing to install.

What risk level is ruff-format? +

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

Can I rate-limit ruff-format? +

Yes. Add a rate_limit block to the ruff-format 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 ruff-format completely? +

Set action: deny in the PolicyLayer policy for ruff-format. 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 ruff-format? +

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

Enforce policy on every Lint tool call.

Start from Lint, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →