# 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-pare-python/black

## Facts

- Tool: `black`
- Server: Python (`Dave-London/Pare`) — https://policylayer.com/tools/io-github-dave-london-pare-python.md
- Homepage: https://github.com/Dave-London/Pare
- Risk category: Read (Low risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 10
- Recommended policy verdict: Allowed

## Parameters

| Parameter | Type | Required | Description |
| --- | --- | --- | --- |
| `diff` | boolean | no | Show diff of changes without applying (--diff) |
| `path` | string | no | Project root path |
| `check` | boolean | no | Check mode (report without modifying files) |
| `config` | string | no | Path to explicit Black config file (--config) |
| `compact` | boolean | no | Prefer compact output |
| `preview` | boolean | no | Enable preview style (--preview) |
| `targets` | array | no | Files or directories to format (default: ["."]) |
| `lineLength` | integer | no | Override the configured line length (--line-length) |
| `targetVersion` | string | no | Python version to target, e.g. 'py310', 'py311', 'py312' (--target-version) |
| `skipStringNormalization` | boolean | no | Skip string quote normalization (-S) |

Parameters from the server's own tool schema.

## 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 Low

Even though black only reads data, uncontrolled read access leaks sensitive information and racks up API costs: an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.

Risk signals: Accepts file system path (path) · High parameter count (10 properties)

## Use case

AI agents call black to retrieve information from Python without modifying anything. It is typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.

## Recommended policy (PolicyLayer)

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

```json
{
  "version": "1",
  "default": "deny",
  "tools": {
    "black": {}
  }
}
```

## Other tools on Python (13)

- `conda` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/conda.md
- `mypy` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/mypy.md
- `pip-install` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/pip-install.md
- `poetry` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/poetry.md
- `pyenv` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/pyenv.md
- `pytest` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/pytest.md
- `ruff-check` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/ruff-check.md
- `uv-install` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/uv-install.md
- `uv-run` — Execute — https://policylayer.com/tools/io-github-dave-london-pare-python/uv-run.md
- `pip-audit` — Read — https://policylayer.com/tools/io-github-dave-london-pare-python/pip-audit.md
- `pip-list` — Read — https://policylayer.com/tools/io-github-dave-london-pare-python/pip-list.md
- `pip-show` — Read — https://policylayer.com/tools/io-github-dave-london-pare-python/pip-show.md
- `ruff-format` — Read — https://policylayer.com/tools/io-github-dave-london-pare-python/ruff-format.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-pare-python · API: https://policylayer.com/registry/api · Policy library: https://policylayer.com/policies/io-github-dave-london-pare-python