Calculator MCP Server

A very basic MCP (Model Context Protocol) server built for training purposes. It exposes five simple tools over stdio so you can see the core MCP mechanics — tool listing, input schemas, and structured responses — without any extra complexity like auth, persistence, or external APIs.

Tools

Related MCP server: MPC-PoC-1-EchoServerToolsbasicas

Setup

npm install
npm run build

Testing locally

Use the MCP Inspector to interactively call each tool from a browser UI:

npm run inspect

This opens a local web page where you can select a tool, fill in arguments, and see the raw JSON-RPC request/response.

Using it in Claude Desktop / Claude Code

Add this to your MCP client's config (e.g. claude_desktop_config.json):

{
  "mcpServers": {
    "calculator": {
      "command": "node",
      "args": ["/Users/douglasbailey/my-dev/claude-mcp/dist/index.js"]
    }
  }
}

Restart the client, and the five calculator tools will be available for Claude to call.

How it works

• src/index.ts creates an MCP Server, declares the tools capability, and connects over StdioServerTransport (the standard transport for local MCP servers).

• ListToolsRequestSchema handler returns the tool definitions (name, description, JSON-schema input).

• CallToolRequestSchema handler dispatches on request.params.name and returns {content: [{type: "text", text: ...}]}.

• Throwing an Error inside a handler (e.g. divide-by-zero) is automatically surfaced to the client as a tool error — no special handling needed.