universal-commerce-protocol/ucp

The Universal Commerce Protocol, or UCP, is an open specification for how different systems in online commerce can talk to each other in a consistent way. Instead of each platform, business, payment provider, and credential provider building custom one off integrations, UCP defines a shared language and a set of building blocks so these systems can discover each other's capabilities and complete transactions reliably. The protocol is built around two ideas: Capabilities and Extensions. Capabilities are core commerce functions a business can implement, such as Checkout or Order, while Extensions add optional enhancements like discounts or fulfillment options without complicating the core definitions. Businesses declare which Capabilities they support in a standardized profile, which lets platforms, including AI shopping agents, automatically discover and configure themselves to work with that business. The initial release focuses on a few essential pieces: Checkout, which handles cart management and tax calculation with or without a human directly present, Identity Linking, which uses OAuth 2.0 to let a platform act on a user's behalf, Order, which delivers webhook based updates as an order is shipped, delivered, or returned, and Payment Token Exchange, which lets payment service providers and credential providers securely swap payment tokens. The protocol is described as transport agnostic, meaning businesses can expose these Capabilities through REST APIs, MCP, or A2A depending on what fits their existing systems. This repository is documentation and specification focused rather than a runnable application. It points to a separate samples repository for implementation examples and a conformance repository for testing whether an implementation follows the spec correctly. The protocol builds on existing open standards where possible, including support for AP2 payment mandates and verifiable credentials, and future plans mentioned in the README include expanding beyond shopping into areas like travel and services, plus adding loyalty program support. UCP is released as an open source project under the Apache 2.0 license.