Show HN: UCP Demo – Interactive Demo of the Universal Commerce Protocol

I built an interactive demo to showcase how the Universal Commerce Protocol (UCP) works.

What is UCP? UCP is an open standard that enables AI agents and platforms to complete purchases on any UCP-enabled merchant without custom integrations.

What the demo shows:

Discovery via /.well-known/ucp - how platforms find merchant capabilities Checkout Sessions API - create, update, and complete purchases Toggle "Debug Mode" to see the actual API calls in real-time

What's implemented vs mocked:

- Discovery endpoint with capabilities and payment handlers - Full checkout flow with line items, buyer info, payment selection - Payment processing uses test tokens (no real charges) - In-memory storage (resets on each session)

Links:

Demo: https://ucp-demo.web.app

UCP Spec: https://ucp.dev

Source: https://github.com/hemanth/ucp-demo

Would love feedback on the developer experience. Is the protocol discoverable enough? What's missing?