mcp-builder

name	mcp-builder
description	Guide for building Model Context Protocol (MCP) servers and tools

MCP Server Builder

Instructions

When the user asks you to build an MCP server, MCP tool, or integrate with the Model Context Protocol:

1. MCP Server Structure — an MCP server exposes tools to LLM agents via a standardized protocol
2. Communication — uses JSON-RPC 2.0 over stdio (default) or SSE
3. Tools — each tool has a name, description, and JSON Schema for parameters

Server Template

import { Server } from '@modelcontextprotocol/sdk/server/index.js';
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';

const server = new Server({ name: 'my-server', version: '1.0.0' }, {
  capabilities: { tools: {} }
});

server.setRequestHandler(ListToolsRequestSchema, async () => ({
  tools: [{
    name: 'my_tool',
    description: 'Does something useful',
    inputSchema: {
      type: 'object',
      properties: {
        input: { type: 'string', description: 'The input' }
      },
      required: ['input']
    }
  }]
}));

server.setRequestHandler(CallToolRequestSchema, async (request) => {
  const { name, arguments: args } = request.params;
  if (name === 'my_tool') {
    return { content: [{ type: 'text', text: 'result' }] };
  }
  throw new Error(`Unknown tool: ${name}`);
});

const transport = new StdioServerTransport();
await server.connect(transport);

Best Practices

• Keep tool descriptions clear and concise
• Use strict JSON Schema validation
• Handle errors gracefully, return error content blocks
• Log to stderr (stdout is the protocol channel)
• Test tools independently before connecting via MCP