Building a Price Monitoring Tool with Claude Code
So far, I’ve built a number guessing game, a to-do list, and a budgeting app using Claude Code. This time, I’m taking it up a notch with a more practical project: a price monitoring tool.
You know that feeling when you want something but the price is too high? Wouldn’t it be great to have a tool that automatically alerts you when the price drops? I built exactly that through a conversation with Claude Code.
What We’re Building: A Price Monitoring Tool
Key Features
- Product URL Registration: Register product URLs along with your target price
- Automatic Price Checks: Periodically fetches and records current prices
- Price Drop Notifications: Alerts you when the price falls below your target
- Price History Charts: Visualize price trends with graphs
- Multi-Site Support: Works with major e-commerce sites like Amazon and Rakuten
Conversation with Claude Code
I started by asking Claude Code to “build a tool that monitors prices of items I want to buy and notifies me when they get cheaper.”
Claude Code proposed the following features:
- Fetch price data from product URLs
- Save price history to JSON files
- Compare against target prices
- Display price trend graphs
Implementation Walkthrough
1. Product Registration
Register the URL and target price for the products you want to monitor.
2. Automatic Price Fetching
Claude Code wrote the price-scraping logic using requests and BeautifulSoup.
It handles the different price display patterns for major e-commerce sites (Amazon, Rakuten, and Yahoo! Shopping).
3. Price History Management
Fetched prices are saved to a JSON file along with timestamps. This makes it possible to track price trends over time.
4. Notification System
When a price drops below the target value, a notification is displayed in the console. In the future, this could be extended to support email or LINE notifications.
Price Trend Graph
Using matplotlib, you can visualize price trends in a graph.
The horizontal axis shows dates, and the vertical axis shows prices, making price changes easy to see at a glance. The target price is shown as a dashed line, so you can quickly tell how close the current price is to your buy point.
My Impressions After Using It
What’s Great
- Automated price checking: No more manually checking prices every day
- Never miss a deal: Get notified as soon as the price hits your target
- Manage multiple items at once: Monitor your entire wish list in one place
- Price history visibility: Spot sale patterns and trends
Room for Improvement
- Add more notification methods (email, LINE, etc.)
- Automate scheduled runs (cron or Task Scheduler)
- Support more e-commerce sites
- Fetch additional info beyond price (stock status, etc.)
Conclusion
Using Claude Code, I was able to build a practical price monitoring tool from scratch.
Web scraping might sound intimidating, but by working through it conversationally with Claude Code, even a beginner can get it done. Claude Code handles the differences in HTML structure across different sites seamlessly.
Next time, I’d like to take this tool further by adding automated scheduling and email notification features.
Until next time!
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