MCP (Model Context Protocol): a complete overview — how to connect AI to your data

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

// stock lives in your system; here it is a small table for the example
const stock: Record<string, number> = { 'A-100': 8, 'B-200': 0 };

const server = new McpServer({ name: 'shop', version: '1.0.0' });

// a tool: the assistant may call it, and the schema checks the arguments
server.registerTool(
  'get_stock',
  {
    title: 'Stock by SKU',
    description: 'How many items of a product are in stock',
    inputSchema: { sku: z.string().describe('Product SKU, for example A-100') },
    annotations: { readOnlyHint: true },
  },
  async ({ sku }) => {
    const qty = stock[sku];
    const text = qty === undefined ? `No product ${sku}` : `${sku}: ${qty} pcs`;
    return { content: [{ type: 'text', text }] };
  },
);

await server.connect(new StdioServerTransport());

import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js';
import { StdioServerTransport } from '@modelcontextprotocol/sdk/server/stdio.js';

const server = new McpServer({ name: 'docs', version: '1.0.0' });

// a resource: a document the assistant can read but cannot change
server.registerResource(
  'delivery-terms',
  'docs://delivery-terms',
  { title: 'Delivery terms', mimeType: 'text/markdown' },
  async (uri) => ({
    contents: [{ uri: uri.href, text: '# Delivery\nCourier: 1–2 days. Pickup: the same day.' }],
  }),
);

await server.connect(new StdioServerTransport());

{
  "mcpServers": {
    "shop": {
      "command": "node",
      "args": ["/srv/mcp/shop.js"],
      "env": { "SHOP_API_KEY": "key-for-read-only-access" }
    }
  }
}