Building the Universal Commerce Protocol (2026) - Shopify

This post introduces the Universal Commerce Protocol (UCP), an open standard co-developed with Google for AI agents to transact with merchants. It details UCP's layered architecture (Shopping Service, Capabilities, Extensions), discovery and negotiation mechanisms, and how it handles transaction states like `incomplete`, `requires_escalation`, and `ready_for_complete`. It also describes the Embedded Checkout Protocol (ECP) for seamless handoffs and dynamic, two-sided negotiation of payment handlers. The protocol emphasizes namespace binding for security and extensibility, allowing domain-specific extensions without central approval.