Actions
Blocking work named in-band
actions[] lets a business hand the agent a 3DS challenge or form without a dead end.
UCP · 2026-08
Open Cart
Search. Add. That’s the protocol.
Live catalog across Shopify. Add to a real merchant cart. Pay on their site.
Start with a search
Results come back with Add to cart — that call is create_cart on the merchant.
2026-08 edition
What just shipped in the protocol
UCP is an open standard (Shopify + Google), not a Shopify app. Merchants publish /.well-known/ucp. Agents send a profile URL. Capabilities are negotiated. Search and cart above are live MCP calls.
Policies
Terms on the response
policies[] with JSONPath applies_to — storewide default, line-item override.
Identity
Buyer + agent, one request
OAuth for the buyer, RFC 9421 signature for the agent. No extra browser login if both sides support it.
Locations
Physical search
Find a store by radius, hours, and amenities, then pass selected_destination_id into checkout.
Money
Split pay and terms
Gift card + points + card on one checkout. Deposit now, remainder later.
Measure
Sell by weight
Fractional quantity and sale-basis pricing for grocery and any non-integer SKU.
Do this now
Storefront MCP cart tools get_cart / update_cart on /api/mcp stop on 31 Aug 2026. Move to /api/ucp/mcp with create_cart, get_cart, update_cart, cancel_cart and an agent profile on every call.