Windows Command Line MCP Server

Instructions

Implementation Reference

• index.ts:454-513 (handler)

  The core handler logic for the 'execute_command' tool. It performs security checks to block dangerous commands, constructs the shell command using cmd.exe on Windows, sets execution options, calls the executeCommand helper, and returns stdout or an error.

  async ({ command, workingDir, timeout }) => {
    try {
      // Security check: Ensure only allowed commands are executed
      const commandLower = command.toLowerCase();
      
      // Block potentially dangerous commands
      const dangerousPatterns = [
        'net user', 'net localgroup', 'netsh', 'format', 'rd /s', 'rmdir /s', 
        'del /f', 'reg delete', 'shutdown', 'taskkill', 'sc delete', 'bcdedit',
        'cacls', 'icacls', 'takeown', 'diskpart', 'cipher /w', 'schtasks /create',
        'rm -rf', 'sudo', 'chmod', 'chown', 'passwd', 'mkfs', 'dd'
      ];
      
      // Check for dangerous patterns
      if (dangerousPatterns.some(pattern => commandLower.includes(pattern.toLowerCase()))) {
        return {
          isError: true,
          content: [
            {
              type: "text",
              text: "Command contains potentially dangerous operations and cannot be executed.",
            },
          ],
        };
      }
      
      const options: any = { timeout };
      if (workingDir) {
        options.cwd = workingDir;
      }
      
      let cmdToExecute;
      if (isWindows) {
        cmdToExecute = `cmd.exe /c ${command}`;
      } else {
        // For non-Windows, try to execute the command directly
        cmdToExecute = command;
      }
      
      const stdout = executeCommand(cmdToExecute, options);
      return {
        content: [
          {
            type: "text",
            text: stdout.toString() || 'Command executed successfully (no output)',
          },
        ],
      };
    } catch (error) {
      return {
        isError: true,
        content: [
          {
            type: "text",
            text: `Error executing command: ${error}`,
          },
        ],
      };
    }
  }

• index.ts:449-453 (schema)

  Input schema using Zod for the 'execute_command' tool, defining parameters: command (required string), workingDir (optional string), timeout (optional number with default).

  {
    command: z.string().describe("The command to execute"),
    workingDir: z.string().optional().describe("Working directory for the command"),
    timeout: z.number().default(30000).describe("Timeout in milliseconds"),
  },

• index.ts:446-514 (registration)

  MCP server registration of the 'execute_command' tool, including the tool name, description, input schema, and inline handler function.

  server.tool(
    "execute_command",
    "Execute a Windows command and return its output. Only commands in the allowed list can be executed. This tool should be used for running simple commands like 'dir', 'echo', etc.",
    {
      command: z.string().describe("The command to execute"),
      workingDir: z.string().optional().describe("Working directory for the command"),
      timeout: z.number().default(30000).describe("Timeout in milliseconds"),
    },
    async ({ command, workingDir, timeout }) => {
      try {
        // Security check: Ensure only allowed commands are executed
        const commandLower = command.toLowerCase();
        
        // Block potentially dangerous commands
        const dangerousPatterns = [
          'net user', 'net localgroup', 'netsh', 'format', 'rd /s', 'rmdir /s', 
          'del /f', 'reg delete', 'shutdown', 'taskkill', 'sc delete', 'bcdedit',
          'cacls', 'icacls', 'takeown', 'diskpart', 'cipher /w', 'schtasks /create',
          'rm -rf', 'sudo', 'chmod', 'chown', 'passwd', 'mkfs', 'dd'
        ];
        
        // Check for dangerous patterns
        if (dangerousPatterns.some(pattern => commandLower.includes(pattern.toLowerCase()))) {
          return {
            isError: true,
            content: [
              {
                type: "text",
                text: "Command contains potentially dangerous operations and cannot be executed.",
              },
            ],
          };
        }
        
        const options: any = { timeout };
        if (workingDir) {
          options.cwd = workingDir;
        }
        
        let cmdToExecute;
        if (isWindows) {
          cmdToExecute = `cmd.exe /c ${command}`;
        } else {
          // For non-Windows, try to execute the command directly
          cmdToExecute = command;
        }
        
        const stdout = executeCommand(cmdToExecute, options);
        return {
          content: [
            {
              type: "text",
              text: stdout.toString() || 'Command executed successfully (no output)',
            },
          ],
        };
      } catch (error) {
        return {
          isError: true,
          content: [
            {
              type: "text",
              text: `Error executing command: ${error}`,
            },
          ],
        };
      }
    }
  );

• index.ts:17-47 (helper)

  Supporting helper function executeCommand that performs the actual command execution using Node.js execSync, with platform-specific handling (direct exec on Windows, modified fallback on other platforms).

  function executeCommand(command: string, options: any = {}) {
    if (isWindows) {
      return execSync(command, options);
    } else {
      // Log warning for non-Windows environments
      console.error(`Warning: Running in a non-Windows environment (${platform()}). Windows commands may not work.`);
      
      // For testing purposes on non-Windows platforms
      try {
        // For Linux/MacOS, we'll strip cmd.exe and powershell.exe references
        let modifiedCmd = command;
        
        // Replace cmd.exe /c with empty string
        modifiedCmd = modifiedCmd.replace(/cmd\.exe\s+\/c\s+/i, '');
        
        // Replace powershell.exe -Command with empty string or a compatible command
        modifiedCmd = modifiedCmd.replace(/powershell\.exe\s+-Command\s+("|')/i, '');
        
        // Remove trailing quotes if we removed powershell -Command
        if (modifiedCmd !== command) {
          modifiedCmd = modifiedCmd.replace(/("|')$/, '');
        }
        
        console.error(`Attempting to execute modified command: ${modifiedCmd}`);
        return execSync(modifiedCmd, options);
      } catch (error) {
        console.error(`Error executing modified command: ${error}`);
        return Buffer.from(`This tool requires a Windows environment. Current platform: ${platform()}`);
      }
    }
  }