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Universal Commerce Protocol (UCP): Discovery, Capabilities and Checkout for Agents

Guide · updated 2026-10-15 · Markdown variant

UCP is an open, Apache-2.0 standard for commerce interoperability between platforms and businesses: the /.well-known/ucp profile, capability naming, transport bindings, payment handlers, and how it relates to ACP, AP2, MCP and A2A.

The Universal Commerce Protocol (UCP) is an open standard for interoperability between commerce entities, so agent platforms can run catalog, cart and checkout flows against businesses through one profile format. Decision rule: if you build a shopping agent or a merchant endpoint, read the business profile at /.well-known/ucp first; it tells you which services, capabilities, transports and payment handlers exist.

Key facts

• Core capabilities listed on ucp.dev: Catalog, Cart, Checkout, Identity Linking, Order.
• Transports: REST and JSON-RPC, with MCP and A2A support. The transport enum is rest, mcp, a2a, embedded.
• Licence: Apache 2.0. Repository: https://github.com/Universal-Commerce-Protocol/ucp
• ucp.dev lists Google, Shopify, Etsy, Amazon and others under "Co-developed by industry leaders"; the copyright line credits "UCP Authors".

How does discovery and naming work?

• Businesses publish a profile at /.well-known/ucp. Platforms publish theirs at the URI sent in the UCP-Agent header.
• Both profile types must carry ucp.version, ucp.services and ucp.payment_handlers; the registries must be present even when empty.
• A service defines the API surface for a vertical; a capability is a feature within a service; an extension is an optional module that augments a capability via extends.
• Capability names are {reverse-domain}.{service}.{capability}, e.g. dev.ucp.shopping.checkout. dev.ucp.* is reserved for the UCP governing body.
• Entity versions are YYYY-MM-DD dates (e.g. 2026-08-25); protocol version selection is separate from capability negotiation. Amounts are minor units (cents).

How does checkout and payment work?

• The checkout capability exposes create_checkout, update_checkout, complete_checkout.
• Payment handlers are advertised in the payment_handlers registry (fields include id, version, spec, schema, available_instruments, config); a business can order them with map_order as a non-binding preference.
• For autonomous-agent scenarios UCP supports the Agent Payments Protocol (AP2) through the optional dev.ucp.common.payment.ap2_mandate extension: payment mandates and verifiable credentials, with cryptographic proof of user consent. Businesses stay Merchant of Record.

How does it relate to other protocols?

UCP is a commerce-semantics layer that can ride on MCP or A2A transports (see /resources/mcp-vs-a2a, /resources/a2a-protocol) and supports AP2 through an optional mandates extension. The Agentic Commerce Protocol and AP2 are compared in /resources/agentic-payment-protocols. Caveat: versions are dated (YYYY-MM-DD); pin to a dated release rather than latest and check ucp.dev before depending on field names.

See also: /resources/agentic-payment-protocols, /resources/selling-to-agents, /resources/agent-wallets-x402

Sources

• UCP home, fetched 2026-10-15: https://ucp.dev
• UCP specification overview, fetched 2026-10-15: https://ucp.dev/latest/specification/overview/
• Repository, fetched 2026-10-15: https://github.com/Universal-Commerce-Protocol/ucp

#ucp #agentic-commerce #protocols #checkout #agents #ap2

Category: Guide