MCP server starter

The code

Two files, exactly what you get in the editor.

import express from 'express'
import { McpServer } from '@modelcontextprotocol/sdk/server/mcp.js'
import { StreamableHTTPServerTransport } from '@modelcontextprotocol/sdk/server/streamableHttp.js'
import { z } from 'zod'

// Each request gets a fresh, stateless server. Add your own tools below.
function tools() {
  const server = new McpServer({ name: 'jsdrop-tools', version: '1.0.0' })

  server.registerTool(
    'roll_dice',
    {
      title: 'Roll dice',
      description: 'Roll a number of dice with the given number of sides.',
      inputSchema: { count: z.number().int().min(1).max(20), sides: z.number().int().min(2).max(100) },
    },
    async ({ count, sides }) => {
      const rolls = Array.from({ length: count }, () => 1 + Math.floor(Math.random() * sides))
      return { content: [{ type: 'text', text: `Rolled ${rolls.join(', ')} (total ${rolls.reduce((a, b) => a + b, 0)})` }] }
    },
  )

  server.registerTool(
    'word_count',
    {
      title: 'Count words',
      description: 'Count the words and characters in a text.',
      inputSchema: { text: z.string() },
    },
    async ({ text }) => ({
      content: [{ type: 'text', text: JSON.stringify({ words: text.split(/\s+/).filter(Boolean).length, characters: text.length }) }],
    }),
  )
  return server
}

const app = express()
app.use(express.json())

app.get('/', (req, res) => {
  const endpoint = `${req.protocol}://${req.get('host')}/mcp`
  res.type('html').send(`<h1>MCP tool server</h1>
<p>Point your MCP client at <code>${endpoint}</code> (Streamable HTTP).</p>`)
})

app.post('/mcp', async (req, res) => {
  const server = tools()
  const transport = new StreamableHTTPServerTransport({ sessionIdGenerator: undefined })
  res.on('close', () => {
    transport.close()
    server.close()
  })
  await server.connect(transport)
  await transport.handleRequest(req, res, req.body)
})

const port = Number(process.env.PORT) || 3000
app.listen(port, () => console.log(`MCP server on port ${port}, endpoint /mcp`))

{
  "name": "mcp-tools",
  "private": true,
  "type": "module",
  "dependencies": {
    "@modelcontextprotocol/sdk": "^1.20.0",
    "express": "^5.1.0",
    "zod": "^3.25.0"
  }
}