What is the Universal Commerce Protocol (UCP)?

UCP has two sides (UCP specification overview, read October 29, 2026):

• Businesses (stores) publish a profile at /.well-known/ucp. It is a JSON file that lists the UCP version, the services and capabilities the business supports, and its payment handlers. It can also carry signing keys.
• Platforms (the apps and agents that shop for a buyer) publish a profile of their own and include its URL in every request.

When a platform makes a request, the business compares the two profiles and keeps the capabilities both sides support, at the highest version both support. If there is no overlap, it returns an error such as version_unsupported or capabilities_incompatible.

There is no central sign-up. The spec calls this "permissionless onboarding": any platform with a discoverable profile can interact with any business "without prior registration". A business can still keep its own list of approved platforms and set its own access rules.

The spec also names a third role, the payment credential provider, which issues payment tokens. The platform gets a token from the provider and passes it to the business, and the spec says platforms should not touch raw financial credentials.

A capability is a named part of the protocol that a business or platform can support. Names use reverse-domain form, such as dev.ucp.shopping.checkout, so no central registry of names is needed (UCP specification overview, read October 29, 2026).

Extensions add to a capability. The spec names fulfillment (added to checkout), discount (added to checkout and cart) and AP2 mandates, an optional extension for cryptographic payment authorization. An extension is dropped when its parent capability isn't in use.

The UCP site describes these as covering the purchase from discovery to after the sale, and says an agent can either hand a cart off to the store's website or check out in place (ucp.dev, read October 29, 2026).

Each service in a business's profile names a transport. The spec defines four (UCP specification overview, read October 29, 2026):

• REST, the core transport: an HTTP API described with OpenAPI. The platform puts a link to its profile in the UCP-Agent request header.
• MCP (Model Context Protocol): UCP operations offered as tools an AI model can call, described with OpenRPC. The platform puts a link to its profile in a meta object in the tool call's arguments.
• A2A (Agent2Agent): described with an Agent Card.
• Embedded: also described with OpenRPC.

A business chooses which transports to offer, and a platform connects over one the business lists. The capabilities are the same whichever transport carries them.

The Agentic Commerce Protocol (ACP) is another open standard for agent shopping. Its README calls it "an interaction model and open standard for connecting buyers, their AI agents, and businesses". OpenAI and Stripe are its founding maintainers, it is licensed Apache 2.0, and it is in beta (ACP on GitHub, read October 29, 2026).

What they share. Both are open, both cover checkout, and both keep the store as the seller: UCP says merchants stay the Merchant of Record (ucp.dev), and ACP says agents let users buy "without being the merchant of record".

How each describes itself:

Nothing in either spec stops a store from supporting both. For how UCP and ACP sit alongside AP2, MCP, the Personal Agent Protocol and the card networks' programs, see Agentic commerce protocols explained.

A gift is bought by one person for another, usually shipped to a different address and often needed by a set date. UCP's parts map onto those steps:

• Catalog search finds the gift at the store.
• A checkout session works out the real price, with tax and shipping, before anyone approves the spend.
• The fulfillment extension carries the shipping details.
• Order updates report status and shipment tracking, so the sender knows when the gift arrives.

Because stores publish what they support and agents connect without prior registration, a gifting agent can shop many stores through one standard instead of a custom integration for each. The store stays the seller, so the gift is a normal order from that store. See what is agentic gifting.

Gratos supports UCP.