MCP File System

Implementation Reference

• src/index.ts:52-74 (handler)

  The handler function for the 'read_multiple_files' tool. It validates each file path, reads the contents using fs.readFile, handles individual file errors with Promise.allSettled, formats the output as text, and returns it in the expected MCP format.

  async ({ paths }: { paths: string[] }) => {
      const results = await Promise.allSettled(
          paths.map(async (filePath: string) => {
              try {
                  const validPath = validatePath(filePath);
                  const content = await fs.readFile(validPath, 'utf-8');
                  return { path: filePath, content, success: true };
              } catch (error: any) {
                  return { path: filePath, error: error.message, success: false };
              }
          })
      );
  
      const output = results.map(result => {
          if (result.status === 'fulfilled') {
              return `${result.value.path}: ${result.value.success ? 
                  result.value.content : `Error: ${result.value.error}`}`;
          }
          return `Error processing file: ${result.reason}`;
      }).join('\n\n');
  
      return { content: [{ type: 'text', text: output }] };
  }

• src/index.ts:51-51 (schema)

  The input schema for the 'read_multiple_files' tool, specifying an array of file paths.

  { paths: z.array(z.string()).describe("Array of file paths to read") },

• src/index.ts:49-75 (registration)

  The registration of the 'read_multiple_files' tool using server.tool, including name, schema, and handler reference.

  server.tool(
      "read_multiple_files",
      { paths: z.array(z.string()).describe("Array of file paths to read") },
      async ({ paths }: { paths: string[] }) => {
          const results = await Promise.allSettled(
              paths.map(async (filePath: string) => {
                  try {
                      const validPath = validatePath(filePath);
                      const content = await fs.readFile(validPath, 'utf-8');
                      return { path: filePath, content, success: true };
                  } catch (error: any) {
                      return { path: filePath, error: error.message, success: false };
                  }
              })
          );
  
          const output = results.map(result => {
              if (result.status === 'fulfilled') {
                  return `${result.value.path}: ${result.value.success ? 
                      result.value.content : `Error: ${result.value.error}`}`;
              }
              return `Error processing file: ${result.reason}`;
          }).join('\n\n');
  
          return { content: [{ type: 'text', text: output }] };
      }
  );

• src/index.ts:14-20 (helper)

  Helper function validatePath used by the handler to ensure file paths are within allowed directories before reading.

  function validatePath(filePath: string): string {
      const absolutePath = path.resolve(filePath);
      if (!allowedDirs.some(dir => absolutePath.startsWith(path.resolve(dir)))) {
          throw new Error(`Access denied: ${filePath} is not within allowed directories`);
      }
      return absolutePath;
  }