Cursor Agent MCP Server

Instructions

Implementation Reference

• server.js:386-394 (handler)

  The execution handler for the 'cursor_agent_raw' MCP tool. It extracts parameters from args and invokes the core 'invokeCursorAgent' helper with print disabled for raw access.

  async (args) => {
    try {
      const { argv, output_format, cwd, executable, model, force } = args;
      // For raw calls we disable implicit --print to allow commands like "--help"
      return await invokeCursorAgent({ argv, output_format, cwd, executable, model, force, print: false });
    } catch (e) {
      return { content: [{ type: 'text', text: `Invalid params: ${e?.message || e}` }], isError: true };
    }
  },

• server.js:382-395 (registration)

  MCP tool registration call using server.tool() for 'cursor_agent_raw', specifying name, description, input schema, and handler function.

  server.tool(
   'cursor_agent_raw',
   'Advanced: provide raw argv array to pass after common flags (e.g., ["search","--query","foo"]).',
   RAW_SCHEMA.shape,
   async (args) => {
     try {
       const { argv, output_format, cwd, executable, model, force } = args;
       // For raw calls we disable implicit --print to allow commands like "--help"
       return await invokeCursorAgent({ argv, output_format, cwd, executable, model, force, print: false });
     } catch (e) {
       return { content: [{ type: 'text', text: `Invalid params: ${e?.message || e}` }], isError: true };
     }
   },
  );

• server.js:268-273 (schema)

  Zod schema defining inputs for 'cursor_agent_raw': required argv array, optional print flag, and shared COMMON fields like output_format, cwd, etc.

  const RAW_SCHEMA = z.object({
    // raw argv to pass after common flags; e.g., ["--help"] or ["subcmd","--flag"]
    argv: z.array(z.string()).min(1, 'argv must contain at least one element'),
    print: z.boolean().optional(),
    ...COMMON,
  });

• server.js:38-149 (helper)

  Core utility function invoked by the handler. Spawns 'cursor-agent' CLI process with argv, adds common flags (--print, --output-format, -m, -f), manages env vars, process lifecycle, stdout/stderr capture, timeouts, and idle termination.

  async function invokeCursorAgent({ argv, output_format = 'text', cwd, executable, model, force, print = true }) {
   const cmd = resolveExecutable(executable);
  
   // Compute model/force from args/env
   const userArgs = [...(argv ?? [])];
   const hasModelFlag = userArgs.some((a) => a === '-m' || a === '--model' || /^(?:-m=|--model=)/.test(String(a)));
   const envModel = process.env.CURSOR_AGENT_MODEL && process.env.CURSOR_AGENT_MODEL.trim();
   const effectiveModel = model?.trim?.() || envModel;
  
   const hasForceFlag = userArgs.some((a) => a === '-f' || a === '--force');
   const envForce = (() => {
     const v = (process.env.CURSOR_AGENT_FORCE || '').toLowerCase();
     return v === '1' || v === 'true' || v === 'yes' || v === 'on';
   })();
   const effectiveForce = typeof force === 'boolean' ? force : envForce;
  
   const finalArgv = [
     ...(print ? ['--print', '--output-format', output_format] : []),
     ...userArgs,
     ...(hasForceFlag || !effectiveForce ? [] : ['-f']),
     ...(hasModelFlag || !effectiveModel ? [] : ['-m', effectiveModel]),
   ];
  
   return new Promise((resolve) => {
     let settled = false;
     let out = '';
     let err = '';
     let idleTimer = null;
     let killedByIdle = false;
  
     const cleanup = () => {
       if (mainTimer) clearTimeout(mainTimer);
       if (idleTimer) clearTimeout(idleTimer);
     };
  
     if (process.env.DEBUG_CURSOR_MCP === '1') {
       try {
         console.error('[cursor-mcp] spawn:', cmd, ...finalArgv);
       } catch {}
     }
  
     const child = spawn(cmd, finalArgv, {
       shell: false, // safer across platforms; rely on PATH/PATHEXT
       cwd: cwd || process.cwd(),
       env: process.env,
     });
     try { child.stdin?.end(); } catch {}
  
     const idleMs = Number.parseInt(process.env.CURSOR_AGENT_IDLE_EXIT_MS || '0', 10);
     const scheduleIdleKill = () => {
       if (!Number.isFinite(idleMs) || idleMs <= 0) return;
       if (idleTimer) clearTimeout(idleTimer);
       idleTimer = setTimeout(() => {
         killedByIdle = true;
         try { child.kill('SIGKILL'); } catch {}
       }, idleMs);
     };
  
     child.stdout.on('data', (d) => {
       out += d.toString();
       scheduleIdleKill();
     });
  
     child.stderr.on('data', (d) => {
       err += d.toString();
     });
  
     child.on('error', (e) => {
       if (settled) return;
       settled = true;
       cleanup();
       if (process.env.DEBUG_CURSOR_MCP === '1') {
         try { console.error('[cursor-mcp] error:', e); } catch {}
       }
       const msg =
         `Failed to start "${cmd}": ${e?.message || e}\n` +
         `Args: ${JSON.stringify(finalArgv)}\n` +
         (process.env.CURSOR_AGENT_PATH ? `CURSOR_AGENT_PATH=${process.env.CURSOR_AGENT_PATH}\n` : '');
       resolve({ content: [{ type: 'text', text: msg }], isError: true });
     });
  
     const defaultTimeout = 30000;
     const timeoutMs = Number.parseInt(process.env.CURSOR_AGENT_TIMEOUT_MS || String(defaultTimeout), 10);
     const mainTimer = setTimeout(() => {
       try { child.kill('SIGKILL'); } catch {}
       if (settled) return;
       settled = true;
       cleanup();
       resolve({
         content: [{ type: 'text', text: `cursor-agent timed out after ${Number.isFinite(timeoutMs) ? timeoutMs : defaultTimeout}ms` }],
         isError: true,
       });
     }, Number.isFinite(timeoutMs) ? timeoutMs : defaultTimeout);
  
     child.on('close', (code) => {
       if (settled) return;
       settled = true;
       cleanup();
       if (process.env.DEBUG_CURSOR_MCP === '1') {
         try { console.error('[cursor-mcp] exit:', code, 'stdout bytes=', out.length, 'stderr bytes=', err.length); } catch {}
       }
       if (code === 0 || (killedByIdle && out)) {
         resolve({ content: [{ type: 'text', text: out || '(no output)' }] });
       } else {
         resolve({
           content: [{ type: 'text', text: `cursor-agent exited with code ${code}\n${err || out || '(no output)'}` }],
           isError: true,
         });
       }
     });
   });
  }