# 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-build/black

## Facts

- Tool: `black`
- Server: Build (`Dave-London/Pare`) — https://policylayer.com/tools/io-github-dave-london-build.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

This tool executes the Black formatter as an external process, which modifies source files in place. While formatting changes are technically reversible via version control, the act of running an external command that rewrites files is an Execute-level action. The blast radius is medium because it can rewrite source code across many files if misused.

From the tool's own definition: "'Runs Black code formatter' — actively executes an external formatting tool that modifies source files on disk"

## Use case

AI agents invoke black to trigger actions in Build. 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 Build:

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

## Other tools on Build (201)

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