MCP Calculator Agent

A simple calculator powered by the Model Context Protocol (MCP) and Ollama. Ask math questions in plain English and get answers.

What is this?

This project connects an AI model (Ollama) to a set of calculator tools via MCP. The AI understands your question, picks the right tool, and returns the result — all through a simple chat interface.

How it works

You  ──>  Agent  ──>  Ollama (AI)  ──>  MCP Server (tools)
              │             │                    │
              │  send msg   │  pick tool call    │  execute math
              │<────────────│<───────────────────│
              │  get answer │  return result     │
              │<────────────│<───────────────────│

• MCP Server — exposes 6 calculator tools (add, subtract, multiply, divide, power, sqrt)
• Agent — middleman that connects Ollama to the MCP server and runs the chat loop
• Ollama — the AI brain that reads your question and decides which tool to use

Prerequisites

• Node.js v18+
• Ollama installed and running

# Pull a model
ollama pull qwen3:4b

Setup

# Install dependencies
npm install

Run

# Interactive chat
npm run dev

Then ask things like:

What is 12 * 15?
What's the square root of 144?
Calculate (3 + 7) * 2
What is 2 to the power of 10?

Type quit or exit to stop.

Available Tools

Tool	Description	Example
add	Add two numbers	3 + 5
subtract	Subtract second from first	10 - 4
multiply	Multiply two numbers	6 * 7
divide	Divide first by second	20 / 4
power	Raise number to a power	2^8
sqrt	Square root of a number	sqrt(144)

Use a different model

Set the OLLAMA_MODEL environment variable:

OLLAMA_MODEL=qwen2.5-coder:3b npm run dev

Integrate with OpenCode

Add this to opencode.jsonc in your project root:

{
  "$schema": "https://opencode.ai/config.json",
  "mcp": {
    "calculator": {
      "type": "local",
      "command": ["npx", "tsx", "src/server-runner.ts"],
      "cwd": "."
    }
  }
}

Project structure

mcp-calculator/
├── src/
│   ├── server.ts         # MCP server with calculator tools
│   ├── server-runner.ts  # Entry point for the MCP server
│   ├── agent.ts          # Agent connecting Ollama to MCP
│   ├── index.ts          # Interactive REPL
│   └── test.ts           # Quick end-to-end test
├── package.json
└── tsconfig.json

License

MIT