Curl MCP Server

Instructions

Implementation Reference

• src/index.ts:224-289 (handler)

  The main handler function for the 'curl_put' tool. Constructs curl command arguments for an HTTP PUT request, handles JSON/data payloads, headers, redirects, and timeout options, executes the command using the shared executeCurl helper, and formats the response.

  async ({ url, data, json_data, headers, content_type, follow_redirects, timeout }) => {
    const args = ['curl'];
    
    // Add the URL
    args.push(url);
    
    // Add PUT method
    args.push('-X', 'PUT');
    
    // Handle data
    if (json_data) {
      args.push('-d', JSON.stringify(json_data));
      if (!content_type) {
        content_type = 'application/json';
      }
    } else if (data) {
      args.push('-d', data);
    }
    
    // Add content type header
    if (content_type) {
      args.push('-H', `Content-Type: ${content_type}`);
    }
    
    // Add additional headers if provided
    if (headers && headers.length > 0) {
      headers.forEach(header => {
        args.push('-H', header);
      });
    }
    
    // Add follow redirects option
    if (follow_redirects) {
      args.push('-L');
    }
    
    // Add timeout if provided
    if (timeout) {
      args.push('--max-time', timeout.toString());
    }
    
    // Include response headers in output
    args.push('-i');
    
    try {
      const result = await executeCurl(args);
      
      return {
        content: [
          {
            type: "text",
            text: `Exit Code: ${result.exitCode}\n\nResponse:\n${result.stdout}${result.stderr ? `\n\nErrors:\n${result.stderr}` : ''}`,
          },
        ],
      };
    } catch (error) {
      return {
        content: [
          {
            type: "text",
            text: `Error executing curl: ${error instanceof Error ? error.message : String(error)}`,
          },
        ],
      };
    }
  }

• src/index.ts:215-223 (schema)

  Input schema validation using Zod for the curl_put tool parameters: URL (required), optional data/JSON payload, headers, content-type, follow redirects, and timeout.

  {
    url: z.string().describe("The URL to make the PUT request to"),
    data: z.string().optional().describe("Data to send in the PUT request body"),
    json_data: z.record(z.any()).optional().describe("JSON object to send as PUT data"),
    headers: z.array(z.string()).optional().describe("Optional HTTP headers in the format 'Header: Value'"),
    content_type: z.string().optional().describe("Content-Type header (will be added automatically for JSON data)"),
    follow_redirects: z.boolean().optional().default(false).describe("Whether to follow redirects"),
    timeout: z.number().optional().describe("Request timeout in seconds"),
  },

• src/index.ts:212-214 (registration)

  Registration of the 'curl_put' tool on the MCP server, specifying name and description.

  server.tool(
    "curl_put",
    "Make an HTTP PUT request using curl",

• src/index.ts:23-62 (helper)

  Shared helper function to safely spawn and execute curl subprocess, capturing stdout/stderr/exit code. Used by all curl tools including curl_put.

  async function executeCurl(args: string[]): Promise<{ stdout: string; stderr: string; exitCode: number }> {
    return new Promise((resolve) => {
      // Ensure we're only calling curl with safe arguments
      if (!args.includes('curl')) {
        args.unshift('curl');
      }
      
      const child = spawn('curl', args.slice(1), {
        stdio: ['pipe', 'pipe', 'pipe'],
        shell: false,
      });
  
      let stdout = '';
      let stderr = '';
  
      child.stdout.on('data', (data) => {
        stdout += data.toString();
      });
  
      child.stderr.on('data', (data) => {
        stderr += data.toString();
      });
  
      child.on('close', (code) => {
        resolve({
          stdout,
          stderr,
          exitCode: code || 0,
        });
      });
  
      child.on('error', (error) => {
        resolve({
          stdout: '',
          stderr: error.message,
          exitCode: 1,
        });
      });
    });
  }