# 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-build/head

## Facts

- Tool: `head`
- Server: Build (`Dave-London/Pare`) — https://policylayer.com/tools/io-github-dave-london-build.md
- 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 read-only operations that retrieve metadata about a resource without modifying or executing anything. The tool has no capability to alter state, trigger actions, or cause side effects beyond retrieving and returning header information.

From the tool's own definition: "Tool performs 'HTTP HEAD request' which retrieves only response headers without a body, used to 'check resource existence, content type, or cache headers'. This is a non-destructive inspection operation with no side effects."

## Use case

AI agents call head to retrieve information from Build 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 Build:

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

## 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
- `black` — Execute — https://policylayer.com/tools/io-github-dave-london-build/black.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
- …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