UCP · Universal Commerce Protocol
Open standard for agent-driven shopping discovery.
UCP standardises how an autonomous agent discovers a merchant, retrieves a quote, and completes checkout on behalf of a human. Merchants publish capabilities at /.well-known/ucp; agents from Google AI Mode and Shopify Sidekick (and any UCP-aware client) consume them. UCP launched January 2026.
The four things UCP actually delivers.
- Defines a /.well-known/ucp discovery surface every merchant publishes.
- Standardises catalog lookup, quote, cart, and checkout primitives.
- Lets any UCP agent buy from any UCP merchant without bespoke glue.
- Powers Google AI Mode shopping and Shopify's agentic surfaces.
The flow, end to end.
User asks
"Buy me running shoes under $100."
Agent discovers
Crawls UCP profiles for Nike, Adidas, etc.
Capability negotiation
Agent + merchant exchange supported actions.
Checkout
Agent completes purchase via Google Pay / Stripe / etc.
Your robot helper knocks on every store's door asking "what do you sell, can I buy it for my human?" The stores hand back menus in a standard format. The robot picks the best match and checks out. That is UCP — a shared menu format for agent shopping.
Get listed in UCP discovery
Merchants on xpay's publisher catalog can publish UCP-compatible profiles, making them discoverable by Google AI Mode and Shopify Sidekick the day they go live.
Publisher catalog →What UCP ships, what it does not, and what bridges the gap.
Open discovery + checkout primitives, Google + Shopify distribution.
No native policy controls (per Nekuda's analysis), no per-agent budget enforcement.
Spending limits, category restrictions, time windows, approval workflows — the enterprise governance UCP explicitly defers.
UCP's missing policy layer
Nekuda's public analysis flags policy as a UCP gap. xpay fills it with 6-dimensional spend controls (budget, category, time, recipient, cumulative, per-transaction) — same controls across UCP and ACP.
Smart Proxy policies →UCP compared.
UCP vs ACP
UCP is open and discovery-first (any agent, any merchant). ACP is Stripe-and-OpenAI-anchored and conversation-first (inside ChatGPT). UCP wants horizontal interop; ACP wants the best in-chat checkout.
UCP vs A2A
A2A is agent-to-agent task delegation. UCP is agent-to-merchant commerce. An A2A delegate often calls UCP merchants under the hood.