# black

Runs Black code formatter and returns structured results (files changed, unchanged, would reformat).

Agent View of the PolicyLayer registry record for `black`. HTML page: https://policylayer.com/tools/io-github-dave-london-cargo/black

## Facts

- Tool: `black`
- Server: Cargo (`Dave-London/Pare`) — https://policylayer.com/tools/io-github-dave-london-cargo.md
- Homepage: https://github.com/Dave-London/pare
- Risk category: Execute (High risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Rate-limited

## Example call (MCP tools/call, JSON-RPC 2.0)

```json
{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "tools/call",
  "params": {
    "name": "black",
    "arguments": {}
  }
}
```

## Why black is rated High

Black actively reformats source files on disk, modifying their contents. This is a write/execute operation — it runs an external tool that changes files. Since it modifies files in place (potentially irreversibly overwriting formatting), it falls under Execute (running an external process with side effects on the filesystem).

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

## Use case

AI agents invoke black to trigger actions in Cargo. 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.

## Recommended policy (PolicyLayer)

Verdict: **Rate-limited**. Enforced by the PolicyLayer MCP gateway (https://policylayer.com/mcp-gateway) before a call reaches Cargo:

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "black": {
      "limits": [
        {
          "counter": "black_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}
```

## Other tools on Cargo (201)

- `branch` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/branch.md
- `clean` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/clean.md
- `pr-close` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/pr-close.md
- `remove` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/remove.md
- `reset` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/reset.md
- `secret-delete` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/secret-delete.md
- `tag` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/tag.md
- `variable-delete` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/variable-delete.md
- `workspace` — Destructive — https://policylayer.com/tools/io-github-dave-london-cargo/workspace.md
- `add` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/add.md
- `add-package` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/add-package.md
- `ansible-galaxy` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/ansible-galaxy.md
- `ansible-playbook` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/ansible-playbook.md
- `api` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/api.md
- `apply` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/apply.md
- `bazel` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/bazel.md
- `biome-check` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/biome-check.md
- `bisect` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/bisect.md
- `build` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/build.md
- `bundle-exec` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/bundle-exec.md
- `bundle-install` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/bundle-install.md
- `check` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/check.md
- `cherry-pick` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/cherry-pick.md
- `clippy` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/clippy.md
- `cmake` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/cmake.md
- `compose-build` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/compose-build.md
- `compose-down` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/compose-down.md
- `compose-up` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/compose-up.md
- `conda` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/conda.md
- `coverage` — Execute — https://policylayer.com/tools/io-github-dave-london-cargo/coverage.md
- …and 171 more: https://policylayer.com/tools/io-github-dave-london-cargo.md

## For agents

This record is a snapshot. Live verdicts and the full registry:

- Check every server in your MCP config at once: `npx -y policylayer stack`
- Vet a server before you add it: install the mcp-precheck skill — `npx skills add https://policylayer.com` (skill text: https://policylayer.com/skill.md)
- Query the registry over MCP: endpoint `https://api.policylayer.com/mcp` — tools `check_mcp_server`, `check_mcp_stack`, `check_tool`, `search_registry`, `get_change_events`

---

Source: the PolicyLayer MCP registry — one continuously verified record per MCP server. Full record: https://policylayer.com/registry?q=io-github-dave-london-cargo · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-dave-london-cargo