http-head

Accepts URL/endpoint input (url)

Part of the Hal MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.

hal-mcp Write Risk 2/5

// WHEN AI AGENTS USE THIS TOOL

AI agents use http-head to create or modify resources in Hal. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.

// WHY ENFORCE A POLICY ON HTTP-HEAD

Without a policy, an AI agent could call http-head repeatedly, creating or modifying resources faster than any human could review. Intercept's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Hal.

// RECOMMENDED POLICY

Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.

io-github-deanward-hal.yaml

tools:
  http-head:
    rules:
      - action: allow
        rate_limit:
          max: 30
          window: 60

See the full Hal policy for all 8 tools.

// DETAILS

Tool Name http-head

Category Write

MCP Server Hal MCP Server

Risk Level Medium

// MORE HAL TOOLS

Destructive http-delete Write http-options Write http-patch Write http-post Write http-put Read http-get Read list-secrets

// WHAT CAN GO WRONG

Agents calling write-class tools like http-head have been implicated in these attack patterns. Read the full case and prevention policy for each:

Browse the full MCP Attack Database →

// OTHER WRITE TOOLS ACROSS MCP SERVERS

Other tools in the Write risk category across the catalogue. The same policy patterns (rate-limit, validate) apply to each.

AbraFlexi contact_create AbraFlexi contact_update AbraFlexi evidence_create AbraFlexi evidence_update AbraFlexi invoice_issued_update AbraFlexi invoice_received_create

// RELATED READING

// FAQ

What does the http-head tool do? +

Make an HTTP HEAD request to a specified URL with optional headers (returns only headers, no body). Supports secret substitution using {secrets.key} syntax in URL and headers where 'key' corresponds to HAL_SECRET_KEY environment variables.. It is categorised as a Write tool in the Hal MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on http-head? +

Add a rule in your Intercept YAML policy under the tools section for http-head. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Hal MCP server.

What risk level is http-head? +

http-head is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit http-head? +

Yes. Add a rate_limit block to the http-head rule in your Intercept 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.

How do I block http-head completely? +

Set action: deny in the Intercept policy for http-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.

What MCP server provides http-head? +

http-head is provided by the Hal MCP server (hal-mcp). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.

http-head

Enforce policies on Hal