http-head
Send an HTTP HEAD request to retrieve headers from a specified URL, optionally including custom headers. Supports secure secret substitution using environment variables for sensitive data.
Instructions
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.
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| headers | No | ||
| url | Yes |
Implementation Reference
- src/index.ts:664-677 (registration)Registration of the 'http-head' MCP tool, including input schema (url: string url, optional headers object) and handler that delegates to shared makeHttpRequest('HEAD', ...).server.registerTool( "http-head", { title: "HTTP HEAD Request", description: "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.", inputSchema: { url: z.string().url(), headers: z.record(z.string()).optional() } }, async ({ url, headers = {} }: { url: string; headers?: Record<string, string> }) => { return makeHttpRequest('HEAD', url, { headers }); } );
- src/index.ts:669-672 (schema)Input schema for 'http-head' tool: requires a valid URL, optional headers as string record.inputSchema: { url: z.string().url(), headers: z.record(z.string()).optional() }
- src/index.ts:343-447 (handler)Core handler function implementing all HTTP tool logic, called by 'http-head' with method='HEAD'. Handles secret substitution, URL allowlisting/blacklisting, fetch request, special HEAD response (headers only, no body), secret redaction in output.async function makeHttpRequest( method: string, url: string, options: { headers?: Record<string, string>; body?: string; queryParams?: Record<string, any>; } = {} ) { try { const { headers = {}, body, queryParams = {} } = options; // First, substitute secrets in URL to get the final URL for validation // We need to do this in two passes to handle URL restrictions properly const processedUrl = substituteSecrets(url, url); // Now substitute secrets in headers, body, and query parameters using the processed URL const processedHeaders = substituteSecretsInObject(headers, processedUrl); const processedBody = body ? substituteSecrets(body, processedUrl) : body; const processedQueryParams = substituteSecretsInObject(queryParams, processedUrl); // Build URL with query parameters const urlObj = new URL(processedUrl); Object.entries(processedQueryParams).forEach(([key, value]) => { if (value !== undefined && value !== null) { urlObj.searchParams.set(key, String(value)); } }); const finalUrl = urlObj.toString(); // Check global URL whitelist/blacklist const urlCheck = isUrlAllowedGlobal(finalUrl); if (!urlCheck.allowed) { throw new Error(urlCheck.reason || 'URL is not allowed'); } const defaultHeaders = { 'User-Agent': 'HAL-MCP/1.0.0', ...processedHeaders }; // Add Content-Type for methods that typically send data if (['POST', 'PUT', 'PATCH'].includes(method.toUpperCase()) && processedBody && !('Content-Type' in processedHeaders)) { (defaultHeaders as any)['Content-Type'] = 'application/json'; } const response = await fetch(finalUrl, { method: method.toUpperCase(), headers: defaultHeaders, body: processedBody }); const contentType = response.headers.get('content-type') || 'text/plain'; let content: string; // HEAD requests don't have a body by design if (method.toUpperCase() === 'HEAD') { content = '(No body - HEAD request)'; } else { try { if (contentType.includes('application/json')) { const text = await response.text(); if (text.trim()) { content = JSON.stringify(JSON.parse(text), null, 2); } else { content = '(Empty response)'; } } else { content = await response.text(); } } catch (parseError) { // If JSON parsing fails, try to get text try { content = await response.text(); } catch (textError) { content = '(Unable to parse response)'; } } } // Redact secrets from response headers and content before returning const redactedHeaders = Array.from(response.headers.entries()) .map(([key, value]) => `${key}: ${redactSecretsFromText(value)}`) .join('\n'); const redactedContent = redactSecretsFromText(content); return { content: [{ type: "text" as const, text: `Status: ${response.status} ${response.statusText}\n\nHeaders:\n${redactedHeaders}\n\nBody:\n${redactedContent}` }] }; } catch (error) { const errorMessage = error instanceof Error ? error.message : 'Unknown error'; const redactedErrorMessage = redactSecretsFromText(errorMessage); return { content: [{ type: "text" as const, text: `Error making ${method.toUpperCase()} request: ${redactedErrorMessage}` }], isError: true }; } }
- src/index.ts:399-402 (helper)HEAD-specific handling in makeHttpRequest: sets content to note no body, processes headers.// HEAD requests don't have a body by design if (method.toUpperCase() === 'HEAD') { content = '(No body - HEAD request)'; } else {