Makes an HTTP HEAD request via curl and returns structured response headers (no body). Use to check resource existence, content type, or cache headers. SECURITY: URLs targeting private/reserved IPs are blocked (SSRF protection). The proxy parameter routes traffic through an external proxy — use o...
Accepts URL/endpoint input (url); Accepts file system path (path); High parameter count (13 properties)
Part of the Http MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.
AI agents use head to create or modify resources in Http. 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.
Without a policy, an AI agent could call 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 Http.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
tools:
head:
rules:
- action: allow
rate_limit:
max: 30
window: 60See the full Http policy for all 4 tools.
Agents calling write-class tools like head have been implicated in these attack patterns. Read the full case and prevention policy for each:
Other tools in the Write risk category across the catalogue. The same policy patterns (rate-limit, validate) apply to each.
Makes an HTTP HEAD request via curl and returns structured response headers (no body). Use to check resource existence, content type, or cache headers. SECURITY: URLs targeting private/reserved IPs are blocked (SSRF protection). The proxy parameter routes traffic through an external proxy — use only with trusted proxies.. It is categorised as a Write tool in the Http MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Add a rule in your Intercept YAML policy under the tools section for head. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Http MCP server.
head is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the 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.
Set action: deny in the Intercept 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 Http MCP server (@paretools/http). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Open source. One binary. Zero dependencies.
npx -y @policylayer/intercept