ucp-embedded-checkout
Installation
SKILL.md
UCP Embedded Checkout Protocol (EP)
Before writing code
Fetch live spec: Web-search site:ucp.dev specification checkout-embedded or fetch https://developers.google.com/merchant/ucp/guides/checkout/embedded for the exact JSON-RPC method definitions, handshake flow, and security requirements.
Conceptual Architecture
When Embedded Checkout Is Used
When a checkout reaches requires_escalation status, the agent cannot resolve the issue via API alone. The checkout response includes a continue_url — the Platform opens this URL in an iframe or webview so the buyer can interact with the merchant's checkout UI directly.
Communication Protocol
The iframe communicates with the host (Platform) using JSON-RPC 2.0 over postMessage. Both sides send and receive structured messages.