MCP Sample Server

A stateless Model Context Protocol (MCP) server built with TypeScript, Express, and the official MCP SDK. Exposes two tools — a calculator and a currency converter — over HTTP JSON-RPC.

Tools

Tool	Description
calculator	Perform basic arithmetic: add, subtract, multiply, divide
currency_converter	Convert amounts between 11 supported currencies using static rates

Supported Currencies

USD, EUR, GBP, JPY, INR, CAD, AUD, CHF, CNY, SGD, AED

Endpoints

Method	Path	Description
POST	/mcp	MCP JSON-RPC endpoint
GET	/health	Health check

Getting Started

Prerequisites

• Node.js 18+
• npm

Install & Run

npm install
npm run dev

Server starts on http://localhost:3000.

Scripts

Script	Command	Description
build	npm run build	Compile TypeScript to dist/
start	npm start	Run compiled output
dev	npm run dev	Build + run in one step

Testing

Health Check

curl http://localhost:3000/health

{ "status": "ok", "tools": ["calculator", "currency_converter"] }

List Tools

curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list","params":{}}'

Calculator — Addition

curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 2,
    "method": "tools/call",
    "params": {
      "name": "calculator",
      "arguments": { "operation": "add", "a": 10, "b": 5 }
    }
  }'

Response: 10 + 5 = 15

Currency Converter — USD to INR

curl -X POST http://localhost:3000/mcp \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": 3,
    "method": "tools/call",
    "params": {
      "name": "currency_converter",
      "arguments": { "amount": 100, "from": "USD", "to": "INR" }
    }
  }'

Response:

100 USD = 8312 INR
Rate: 1 USD = 83.12 INR
(Static demo rates — replace with a live API for production)

PowerShell

$body = @{
  jsonrpc = "2.0"; id = 1; method = "tools/call"
  params  = @{ name = "calculator"; arguments = @{ operation = "multiply"; a = 6; b = 7 } }
} | ConvertTo-Json -Depth 5

Invoke-RestMethod -Uri "http://localhost:3000/mcp" -Method POST -ContentType "application/json" -Body $body

MCP Inspector (GUI)

npx @modelcontextprotocol/inspector

Open the printed URL, set transport to HTTP, and connect to http://localhost:3000/mcp.

Architecture

AI Client (e.g. Claude)
       │
       │  POST /mcp  (JSON-RPC 2.0)
       ▼
  Express HTTP Server (port 3000)
       │
       ▼
  MCP Server — stateless, fresh instance per request
       │
       ├── Tool: calculator
       └── Tool: currency_converter

Each POST to /mcp creates a fresh server + transport pair with no session state, making the server horizontally scalable and easy to deploy.

Project Structure

mcp-sample-server/
├── src/
│   └── index.ts        # Server entry point — tools + HTTP setup
├── dist/               # Compiled output (after build)
├── package.json
└── tsconfig.json

Dependencies

Package	Purpose
@modelcontextprotocol/sdk	MCP server + transport primitives
express	HTTP server
zod	Schema validation for tool inputs
typescript	Type safety