UCP (Universal Commerce Protocol) Documentation
UCP (Universal Commerce Protocol) Documentation
Section titled “UCP (Universal Commerce Protocol) Documentation”Universal Commerce Protocol (UCP) is an open standard for agentic commerce interoperability. It enables AI agents, platforms, and businesses to communicate using a common language for shopping: discovering products, managing checkouts, processing payments, and tracking orders — all without custom integrations.
This documentation is extracted from the official UCP docs at https://ucp.dev/
Table of Contents
Section titled “Table of Contents”Getting Started
Section titled “Getting Started”- Overview — What UCP is and why it exists
- Core Concepts — Participants, capabilities, profiles, and the discovery model
- Versioning — Protocol versioning and capability negotiation
Capabilities
Section titled “Capabilities”Checkout
Section titled “Checkout”- Checkout Overview — Core checkout session lifecycle
- Checkout REST API — HTTP REST binding for checkout
- Checkout MCP Binding — JSON-RPC MCP binding for checkout
- Checkout A2A Binding — Agent-to-Agent binding for checkout
- Embedded Checkout Protocol — Browser-embedded checkout via postMessage
- AP2 Mandates Extension — Cryptographic payment authorization using JWS
- Buyer Consent Extension — GDPR/CCPA consent management
- Discounts Extension — Discount codes and allocation details
- Fulfillment Extension — Shipping and pickup method configuration
- Cart Overview — Shopping cart before checkout conversion
- Cart REST API — HTTP REST binding for cart operations
- Cart MCP Binding — JSON-RPC MCP binding for cart
Catalog
Section titled “Catalog”- Catalog Overview — Product catalog search and lookup
- Catalog Search — Search for products by query, filters, and context
- Catalog Lookup — Retrieve products and variants by identifier
- Catalog REST API — HTTP REST binding for catalog
- Catalog MCP Binding — JSON-RPC MCP binding for catalog
Other Capabilities
Section titled “Other Capabilities”- Order — Post-checkout order management with fulfillment events and webhooks
- Identity Linking — OAuth 2.0 account linking between platforms and businesses
Payment Handlers
Section titled “Payment Handlers”- Payment Handler Guide — Framework for specifying payment handlers
- Payment Handler Template — Starter template for new handler specifications
- Tokenization Guide — Guide for building tokenization payment handlers
Payment Handler Examples
Section titled “Payment Handler Examples”- Processor Tokenizer — Business or PSP runs tokenization and processing
- Platform Tokenizer — Platform tokenizes credentials for businesses and PSPs
- Encrypted Credential Handler — Platform encrypts credentials for business decryption
Security
Section titled “Security”- Message Signatures — RFC 9421 HTTP Message Signatures for authentication and integrity
Reference
Section titled “Reference”- Specification Overview — Full protocol specification: governance, negotiation, profiles
- API Reference — Schema reference for all capability data models and types
Advanced
Section titled “Advanced”- UCP and AP2 — Integration with Agent Payments Protocol for cryptographic trust
- Schema Authoring Guide — Conventions for authoring UCP JSON schemas
- Roadmap — Upcoming priorities and future directions
Key Concepts at a Glance
Section titled “Key Concepts at a Glance”Protocol version: 2026-01-11
Participants:
- Business — Merchant or service provider implementing the UCP server
- Platform — AI agent, assistant, or application acting on behalf of users
Discovery: Businesses publish their capabilities at /.well-known/ucp. Platforms advertise their profile URI in each request via the UCP-Agent header.
Transports: REST (HTTP), MCP (JSON-RPC over HTTP), A2A (Agent-to-Agent), Embedded Checkout (postMessage)
Authentication: RFC 9421 HTTP Message Signatures using ECDSA (P-256/ES256)
Versioning: Date-based (YYYY-MM-DD), with capability intersection negotiation
Quick Links
Section titled “Quick Links”| I want to… | Go to… |
|---|---|
| Understand UCP basics | Getting Started: Overview |
| Implement checkout as a business | Checkout Overview |
| Search products as a platform | Catalog Search |
| Add a payment method | Payment Handler Guide |
| Sign HTTP requests | Message Signatures |
| Add AP2 mandate support | AP2 Mandates Extension |
| Understand the full protocol spec | Specification Overview |