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.
This record as markdown: /tools/io-github-dave-london-build/head.md
What head does on Build
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.
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 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.
Attacks that exploit this kind of access
The rule that runs head safely
PolicyLayer is an MCP gateway: it sits between your AI agents and Build, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For head, this is the rule to start with:
head is read-only, so it stays allowed. Everything else on the server is denied unless you say otherwise.
The button opens the PolicyLayer dashboard: create your workspace, connect Build, apply this rule, and every head call is checked against it from then on.
Questions about 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. It is categorised as a Read tool in the Build MCP Server, which means it retrieves data without modifying state.
Register the Build MCP server in PolicyLayer and add a rule for head: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Build. Nothing to install.
head is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the head rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for head. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
head is provided by the Build MCP server (Dave-London/Pare). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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