{
  "id": "D06",
  "url": "https://cartforagents.com/guides/universal-commerce-protocol",
  "title": "Universal Commerce Protocol (UCP): capabilities, checkout and merchant controls",
  "description": "What the Universal Commerce Protocol covers for merchants: the /.well-known/ucp profile, catalog, cart, checkout and orders, read against a real store profile.",
  "answer": "The Universal Commerce Protocol (UCP) is an open, dated-version standard in which a business publishes a profile at /.well-known/ucp listing the capabilities it supports, such as catalog search, cart, checkout and orders, and each agent platform negotiates which of them to use. A capability in that profile is an offer to negotiate, not permission to buy: the platform, its program rules and each checkout response still decide what happens. On October 27, 2026, four Shopify stores advertised checkout in their profiles while the Shopify Catalog record for every one of their products said native checkout was false.",
  "take": "Read a UCP profile as an offer, not a promise. Four stores we checked advertised checkout while every one of their product records said native checkout was false, so verify the route a shopper actually uses.",
  "summary": "UCP splits shopping into separate capabilities: a public profile, catalog search, cart, checkout, orders. A store can advertise checkout while the route a shopper actually uses still sends them to a cart link. Here is the capability map, the version notes, and a real profile read against a real catalog record.",
  "claims": [
    {
      "text": "The UCP specification says businesses publish their profile at /.well-known/ucp, and that the profile contains the protocol version, services, optional capabilities and payment handlers.",
      "source_title": "Universal Commerce Protocol: Official Specification, Profile Structure",
      "source_url": "https://ucp.dev/specification/overview/",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Living specification; we read the version served as latest (2026-08-25) on our check date."
    },
    {
      "text": "UCP separates protocol version selection from capability negotiation: the business advertises its current version, the platform selects one exact version, and the business determines the active capabilities from the versions both sides advertise. UCP does not prescribe a deprecation schedule.",
      "source_title": "Universal Commerce Protocol: Official Specification, Discovery, Governance, and Negotiation",
      "source_url": "https://ucp.dev/specification/overview/",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Describes the protocol, not how any particular platform applies it."
    },
    {
      "text": "The UCP specification says negotiating an extension does not make every future runtime value trusted, and that a platform may apply its own policy and decline any instance that does not satisfy it.",
      "source_title": "Universal Commerce Protocol: Official Specification, Trust and Execution Boundaries",
      "source_url": "https://ucp.dev/specification/overview/",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Normative text for implementers; it does not list any platform's policies."
    },
    {
      "text": "The UCP catalog specification says catalog responses reflect the business's current terms but are not transactional commitments, and that checkout is authoritative.",
      "source_title": "Universal Commerce Protocol: Catalog capability (2026-08-25)",
      "source_url": "https://ucp.dev/2026-08-25/specification/shopping/catalog/",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Version-specific page; later versions may change the wording."
    },
    {
      "text": "UCP checkout sessions move through documented states, including requires_escalation, where buyer input is needed and the platform hands off to the buyer through a continue_url, and ready_for_complete, where the platform can finalize programmatically.",
      "source_title": "Universal Commerce Protocol: Checkout capability (2026-08-25)",
      "source_url": "https://ucp.dev/2026-08-25/specification/shopping/checkout/",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Lists states; it does not say how often any platform reaches each one."
    },
    {
      "text": "The UCP site lists versions 2026-08-25 (marked latest), 2026-04-08, 2026-01-23 and 2026-01-11, plus a draft, and the GitHub repository is licensed Apache 2.0 with release v2026-08-25 published on August 25, 2026.",
      "source_title": "UCP versions list and GitHub releases",
      "source_url": "https://github.com/Universal-Commerce-Protocol/ucp/releases",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Version list read from https://ucp.dev/versions.json on our check date. A release date is not an adoption date."
    },
    {
      "text": "On October 27, 2026, the /.well-known/ucp profiles of all four sellers behind our humidifier catalog search declared version 2026-08-25 and eleven capabilities, including dev.ucp.shopping.checkout, cart and order, with Google Pay, Shopify card and Shop Pay payment handlers.",
      "source_title": "Cart for Agents: profile fetches, October 27, 2026 (How we checked, this page)",
      "source_url": "https://cartforagents.com/guides/universal-commerce-protocol#how-we-checked",
      "source_date": "2026-10-27",
      "method": "observed",
      "limitation": "Four Shopify stores, fetched once. A profile shows what a store advertises, not what any platform has enabled for it."
    },
    {
      "text": "In the October 26, 2026 Shopify Catalog response for \"humidifier for dry winter air large room quiet top fill\", all 10 returned variants had eligible.native_checkout set to false and a checkout_url pointing to the seller's own cart.",
      "source_title": "Cart for Agents: Shopify agent-catalog snapshot, Oct 26, 2026 (How we checked, this page)",
      "source_url": "https://cartforagents.com/guides/universal-commerce-protocol#how-we-checked",
      "source_date": "2026-10-26",
      "method": "observed",
      "limitation": "One unpersonalized search, first variant only, one day before the profiles were fetched."
    },
    {
      "text": "Shopify's public catalog profile at catalog.shopify.com/.well-known/ucp declared catalog search, catalog lookup and identity linking, but no checkout capability and no payment handlers.",
      "source_title": "Cart for Agents: profile fetches, October 27, 2026 (How we checked, this page)",
      "source_url": "https://cartforagents.com/guides/universal-commerce-protocol#how-we-checked",
      "source_date": "2026-10-27",
      "method": "observed",
      "limitation": "Read once; Shopify may change the profile at any time."
    },
    {
      "text": "Shopify's Global Catalog extension reference defines eligible.native_checkout as whether the variant supports native (non-redirect) checkout.",
      "source_title": "Shopify: Global Catalog extension, Variant fields",
      "source_url": "https://shopify.dev/docs/agents/catalog/global-catalog-extension",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Living reference; it does not say which conditions set the flag to true."
    },
    {
      "text": "Shopify's agent documentation says its MCP tools implement UCP across the buyer journey and that agents build carts, convert them to checkouts, and hand off to the merchant for payment.",
      "source_title": "Shopify: Agents, Understand how Shopify does UCP",
      "source_url": "https://shopify.dev/docs/agents",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Describes Shopify's implementation, not other UCP implementations."
    },
    {
      "text": "Google's Merchant Center help says UCP-powered checkout is available to select merchants, applies to products eligible in the United States, Canada and Australia, and only shows on listings that set native_commerce(checkout_eligibility).",
      "source_title": "Google Merchant Center Help: About the Universal Commerce Protocol (UCP) and UCP-powered checkout feature on Google",
      "source_url": "https://support.google.com/merchants/answer/16837055?hl=en",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Help article; Google's onboarding page gives a narrower, US-first rollout, so treat Canada and Australia as unconfirmed."
    },
    {
      "text": "Google's onboarding help says the UCP integration hub in Merchant Center is rolling out gradually in the U.S., with Australia and Canada to follow next year, and lets merchants select capabilities such as cart transfer to the merchant site, native checkout on Google and identity linking.",
      "source_title": "Google Merchant Center Help: How to onboard to the UCP integration hub in Merchant Center",
      "source_url": "https://support.google.com/merchants/answer/16992327?hl=en",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Rollout statement on a living help page; selection is by Google."
    },
    {
      "text": "Shopify's Catalog requirements say a store must be on the Starter plan or higher and not in private mode, with an exception: on the Agentic plan, products can still be included through agentic storefronts before the online store is published to a paid plan.",
      "source_title": "Shopify Help Center: Requirements for being included in Shopify Catalog",
      "source_url": "https://help.shopify.com/en/manual/shopify-catalog/requirements",
      "source_date": "2026-10-27",
      "method": "documented",
      "limitation": "Catalog inclusion also depends on account standing reviewed over time."
    }
  ],
  "sources": [
    {
      "title": "Universal Commerce Protocol (home page)",
      "url": "https://ucp.dev/",
      "accessed": "2026-10-27"
    },
    {
      "title": "Universal Commerce Protocol: Official Specification",
      "url": "https://ucp.dev/specification/overview/",
      "accessed": "2026-10-27"
    },
    {
      "title": "Universal Commerce Protocol: Catalog capability (2026-08-25)",
      "url": "https://ucp.dev/2026-08-25/specification/shopping/catalog/",
      "accessed": "2026-10-27"
    },
    {
      "title": "Universal Commerce Protocol: Checkout capability (2026-08-25)",
      "url": "https://ucp.dev/2026-08-25/specification/shopping/checkout/",
      "accessed": "2026-10-27"
    },
    {
      "title": "Universal Commerce Protocol on GitHub: Releases",
      "url": "https://github.com/Universal-Commerce-Protocol/ucp/releases",
      "accessed": "2026-10-27"
    },
    {
      "title": "Shopify: Agents",
      "url": "https://shopify.dev/docs/agents",
      "accessed": "2026-10-27"
    },
    {
      "title": "Shopify: Global Catalog extension",
      "url": "https://shopify.dev/docs/agents/catalog/global-catalog-extension",
      "accessed": "2026-10-27"
    },
    {
      "title": "Shopify: Global Catalog MCP",
      "url": "https://shopify.dev/docs/agents/catalog/global-catalog",
      "accessed": "2026-10-27"
    },
    {
      "title": "Shopify Help Center: Requirements for being included in Shopify Catalog",
      "url": "https://help.shopify.com/en/manual/shopify-catalog/requirements",
      "accessed": "2026-10-27"
    },
    {
      "title": "Shopify Help Center: Shopify Catalog and product discovery for agentic storefronts",
      "url": "https://help.shopify.com/en/manual/online-sales-channels/agentic-storefronts/products",
      "accessed": "2026-10-27"
    },
    {
      "title": "Google for Developers: Prepare your Merchant Center account (UCP guide)",
      "url": "https://developers.google.com/merchant/ucp/guides/merchant-center",
      "accessed": "2026-10-27"
    },
    {
      "title": "Google Merchant Center Help: About the Universal Commerce Protocol (UCP) and UCP-powered checkout feature on Google",
      "url": "https://support.google.com/merchants/answer/16837055?hl=en",
      "accessed": "2026-10-27"
    },
    {
      "title": "Google Merchant Center Help: How to onboard to the UCP integration hub in Merchant Center",
      "url": "https://support.google.com/merchants/answer/16992327?hl=en",
      "accessed": "2026-10-27"
    }
  ],
  "limitations": [
    "Checked on 2026-10-27; re-check before acting. UCP versions, Shopify's implementation and Google's rollout all change, sometimes without notice on the pages we cite.",
    "The worked example covers four Shopify stores and one unpersonalized catalog search. It is not a sample of UCP merchants and says nothing about stores on other platforms.",
    "We read public profiles and public catalog responses. We did not run a checkout, sign in as a buyer, or see what any assistant shows shoppers.",
    "The catalog search was taken on October 26 and the profiles on October 27, so a change in between would not show.",
    "The capability map is our reading of the specification for merchants. It is not an official UCP document.",
    "Store and brand names are withheld."
  ],
  "related": [
    "https://cartforagents.com/guides/shopify-agentic-storefronts",
    "https://cartforagents.com/guides/ucp-vs-acp",
    "https://cartforagents.com/guides/agentic-commerce-protocol",
    "https://cartforagents.com/guides/google-ucp-checkout",
    "https://cartforagents.com/research/ucp-catalog-native-checkout-research",
    "https://cartforagents.com/guides/how-to-rank-in-chatgpt"
  ],
  "published": "2026-10-27",
  "updated": "2026-10-27",
  "checked": "2026-10-27",
  "kind": "guide"
}