mcp-leftpad/src/index.js

An MCP server that exposes left-pad as a tool

#!/usr/bin/env node

// Import the required modules
import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';
import { z } from 'zod';

// Create an MCP server
const server = new McpServer({
  name: 'mcp-leftpad',
  version: '1.0.0'
});

// Add the left-pad tool
server.tool(
  'left-pad',
  {
    str: z.string().describe('The string to pad'),
    length: z.number().describe('The target length of the padded string'),
    padStr: z.string().optional().describe('The string to pad with')
  },
  async ({ str, length, padStr = ' ' }) => ({
    content: [{ 
      type: 'text', 
      text: str.padStart(length, padStr) 
    }]
  })
);

// Start receiving messages on stdin and sending messages on stdout
const transport = new StdioServerTransport();
server.connect(transport).catch(error => {
  console.error('Error starting MCP server:', error);
  process.exit(1);
});