Model Context Protocol (MCP): connecting AI to tools

import json

from mcp.server.fastmcp import FastMCP

mcp = FastMCP("brew-and-bean")

MENU = {
    "espresso": {"name": "Espresso", "category": "coffee", "price": 120},
    "cappuccino": {"name": "Cappuccino", "category": "coffee", "price": 180},
    "cold-brew": {"name": "Cold Brew", "category": "coffee", "price": 220},
    "filter-coffee": {"name": "Filter Coffee", "category": "coffee", "price": 80},
    "masala-chai": {"name": "Masala Chai", "category": "tea", "price": 90},
    "croissant": {"name": "Butter Croissant", "category": "bakery", "price": 150},
    "banana-bread": {"name": "Banana Bread", "category": "bakery", "price": 130},
    "veg-sandwich": {"name": "Veg Grilled Sandwich", "category": "food", "price": 160},
}


@mcp.tool()
def get_price(item_id: str) -> str:
    """Get the price in rupees of one menu item, given its id such as 'espresso'."""
    item = MENU.get(item_id)
    if item is None:
        return f"No item with id '{item_id}'. Valid ids: {', '.join(MENU)}"
    return f"{item['name']} costs Rs {item['price']}"


@mcp.tool()
def order_total(item_ids: list[str], quantities: list[int]) -> str:
    """Compute the total in rupees for an order. item_ids and quantities are parallel lists."""
    if len(item_ids) != len(quantities):
        return "item_ids and quantities must have the same length"
    total = 0
    for item_id, qty in zip(item_ids, quantities):
        if item_id not in MENU:
            return f"Unknown item id '{item_id}'. Valid ids: {', '.join(MENU)}"
        if qty < 1:
            return "Quantities must be at least 1"
        total += MENU[item_id]["price"] * qty
    return f"Total: Rs {total}"


@mcp.resource("menu://all")
def full_menu() -> str:
    """The complete menu as JSON."""
    return json.dumps(MENU, indent=2)


@mcp.prompt()
def recommend(taste: str) -> str:
    """A reusable prompt that asks for a menu recommendation."""
    return (
        f"A customer likes: {taste}. Using the menu resource menu://all, "
        "recommend up to 2 items and give each price. Do not invent items."
    )


if __name__ == "__main__":
    mcp.run()  # speaks MCP over stdio by default

import asyncio
import sys

from mcp import ClientSession, StdioServerParameters
from mcp.client.stdio import stdio_client


async def main():
    # sys.executable = the Python you are running now, so the server uses the same environment
    params = StdioServerParameters(command=sys.executable, args=["brew_server.py"])
    async with stdio_client(params) as (read, write):
        async with ClientSession(read, write) as session:
            await session.initialize()

            tools = await session.list_tools()
            for tool in tools.tools:
                print("tool:", tool.name, "-", tool.description)

            result = await session.call_tool(
                "order_total",
                {"item_ids": ["cappuccino", "masala-chai"], "quantities": [2, 1]},
            )
            print("result:", result.content[0].text)

            menu = await session.read_resource("menu://all")
            print("resource starts with:", menu.contents[0].text[:40].replace("\n", " "))


asyncio.run(main())

python client_demo.py

npx @modelcontextprotocol/inspector python brew_server.py

claude mcp add brew-and-bean -- /full/path/to/brew-mcp/.venv/bin/python /full/path/to/brew-mcp/brew_server.py

{
  "mcpServers": {
    "brew-and-bean": {
      "command": "/full/path/to/brew-mcp/.venv/bin/python",
      "args": ["/full/path/to/brew-mcp/brew_server.py"]
    }
  }
}

Using the Brew & Bean tools, tell me the total for 2 cold brews and 3 croissants, and show how you got it. Then tell me which of those two items is cheaper.