Build a Price Comparison Shopping Agent with BuyWhere MCP

AI shopping agents are one of the most practical applications of the Model Context Protocol (MCP). With BuyWhere's MCP server, you can build an agent that searches products, compares prices, and tracks deals across 11M+ products from Amazon, Walmart, Shopee, Lazada, and thousands of other retailers — in under 50 lines of code.

In this tutorial, you'll build a price comparison agent using Python and the langchain-mcp-adapter package.

Prerequisites

• Python 3.10+
• A BuyWhere API key (free — get one at buywhere.ai/api-keys)
• pip install langchain-mcp-adapter httpx

Step 1: Get Your API Key

Sign up at buywhere.ai and navigate to API Keys. Create a new key and save it — you'll need it to authenticate your agent.

Step 2: Connect to BuyWhere MCP

BuyWhere exposes four MCP tools:

Here's how to connect:

import json
import httpx

BUYWHERE_API_URL = "https://api.buywhere.ai/mcp/v1"
API_KEY = "your-api-key-here"

async def search_products(query: str, limit: int = 5):
    """Search products using BuyWhere MCP."""
    async with httpx.AsyncClient() as client:
        response = await client.post(
            f"{BUYWHERE_API_URL}/search",
            headers={"Authorization": f"Bearer {API_KEY}"},
            json={"query": query, "limit": limit}
        )
        return response.json()

Step 3: Build the Agent

Now let's create a ReAct agent that can search and compare prices:

from langchain_mcp_adapter import MCPClient
from langchain.agents import create_react_agent, AgentExecutor
from langchain_openai import ChatOpenAI

# Initialize MCP client pointing to BuyWhere
mcp = MCPClient(
    server_url="https://api.buywhere.ai/mcp/v1",
    headers={"Authorization": f"Bearer {API_KEY}"}
)

# Load tools from MCP
tools = mcp.load_tools()

# Create the agent
llm = ChatOpenAI(model="gpt-4o")
agent = create_react_agent(llm, tools, prompt="You are a shopping assistant.")
executor = AgentExecutor(agent=agent, tools=tools)

# Run a query
result = executor.invoke({
    "input": "Find me the cheapest RTX 4070 GPU across all retailers and compare prices"
})
print(result["output"])

Step 4: Add Price Alerts

Want to know when a product drops to your target price? Use the alert tool:

result = executor.invoke({
    "input": "Set a price alert for Sony WH-1000XM5 headphones — notify me if it drops below $250"
})

What's Next?

• Check the full BuyWhere API docs
• Explore the MCP server on GitHub
• Browse best deals by category