# head

Makes an HTTP HEAD request via curl and returns structured response headers (no body). Use to check resource existence, content type, or cache headers.

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

## Facts

- Tool: `head`
- Server: Docker (`@paretools/docker`) — https://policylayer.com/tools/io-github-dave-london-docker.md
- Install: `npx -y @paretools/docker`
- Homepage: https://github.com/Dave-London/pare
- Risk category: Read (Low risk)
- Registry record: grade F, identity unverified
- Server rate-limited: no
- Parameters: 0
- Recommended policy verdict: Allowed

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

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

## Why head is rated Low

HTTP HEAD requests are safe operations that query server metadata without modifying, executing, or deleting any data. The tool retrieves information only (response headers) and produces no side effects. This is a straightforward Read classification with low severity due to the minimal attack surface of header inspection.

From the tool's own definition: "Tool description explicitly states it 'Makes an HTTP HEAD request via curl and returns structured response headers (no body)'. HEAD requests retrieve only metadata without side effects."

## Use case

AI agents call head to retrieve information from Docker 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 Docker:

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

## Other tools on Docker (201)

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