How UCP Powers Agentic Checkout
> UCP powers agentic checkout by giving AI agents a standardised API path — from adding products to a cart through completing a purchase — that works across any UCP-enabled merchant without custom integration, using either a redirect checkout flow or a native embedded checkout for merchants who need more complex logic.
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What Is UCP Agentic Checkout?
UCP agentic checkout is the capability within the Universal Commerce Protocol that enables an AI agent to complete a purchase on behalf of a buyer, using the merchant's own commerce infrastructure, without requiring the buyer to navigate a website or checkout form. It is the transactional endpoint of the UCP shopping lifecycle: after discovery, search, and product evaluation, checkout is where the intent becomes an order.
Google's UCP implementation guide describes the checkout integration as requiring three core REST endpoints for session creation, updates, and completion, with an optional embedded checkout path for merchants who need complex customisation. Beyond these native checkout endpoints, UCP also supports a redirect checkout model — a simpler path where the agent redirects the buyer to the merchant's own checkout page with cart state pre-loaded. This gives merchants two paths to UCP checkout: a fully programmatic native integration and a lighter-weight redirect that requires no API development.
The UCP Cart API is the precursor to checkout. Before a checkout session begins, an agent uses the Cart API to create and manage a multi-item shopping session — adding products, adjusting quantities, and confirming the basket before initiating checkout. This separation of cart management from checkout mirrors the traditional consumer shopping flow and allows agents to handle complex multi-item purchases without creating a checkout session prematurely.
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How the UCP Cart API Works
The UCP Cart API enables agents to build and manage a shopping basket before checkout is initiated. Key operations include:
Create cart: The agent creates a new cart session for the buyer, specifying the initial items (by `item_id` and quantity). The merchant returns a cart object including the session ID, line items, current pricing, and available fulfillment options.
Update cart: As the buyer adds or removes items, changes quantities, or specifies variant preferences, the agent calls the cart update endpoint. The merchant returns the refreshed cart state with updated line items and pricing.
Get cart: At any point, the agent can retrieve the current cart state by session ID. This enables state recovery after network interruptions or for displaying a summary to the buyer before checkout.
Checkout from cart: When the buyer is ready to purchase, the agent initiates checkout from the existing cart session, transitioning it into a checkout flow. The merchant preserves the cart contents and transitions the session into the checkout lifecycle.
The Cart API is intentionally lightweight — it is designed for exploration and intent formation rather than payment processing. An agent can create and abandon multiple cart sessions without any financial consequence, allowing buyers to explore options freely before committing.
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The Two UCP Checkout Paths
Path 1: Native Checkout (three core REST endpoints)
Native checkout is the fully programmatic path. The merchant implements three REST endpoints: 1. Create checkout session — agent sends items, fulfillment address, and optional cart session ID; merchant returns full session state including payment handler details, line items, fulfillment options, and cost breakdown 2. Update checkout session — agent sends address updates or item changes; merchant recomputes tax and fulfillment cost and returns updated session state 3. Complete checkout session — agent sends payment credentials; merchant processes payment via Google Pay tokenisation and returns order confirmation
Native checkout supports both guest checkout (no account linking required) and account-linked checkout (requires OAuth 2.0 identity linking). Google's implementation guide notes that the integration must be approved by Google before going live on Google AI Mode and Gemini.
Path 2: Redirect Checkout
Redirect checkout is the lighter-weight path. Instead of implementing native checkout endpoints, the merchant provides a URL template that the agent uses to redirect the buyer to the merchant's own checkout page with pre-loaded cart contents. FeedBridge supports redirect checkout as a live capability, auto-enabled with privacy and terms of service URLs. This path requires no API development from the merchant's side and is a viable first step for merchants who want UCP presence while planning a full native checkout integration.
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Key Components of UCP Checkout
| Component | Description | Path | |---|---|---| | Cart API — create | Initialise multi-item cart session | Both paths | | Cart API — update | Add/remove items, adjust quantities | Both paths | | Cart API — get | Retrieve current cart state by session ID | Both paths | | Cart API — checkout | Transition cart to checkout | Native path | | Create checkout session | Start checkout with items and address | Native path | | Update checkout session | Refresh session with address/item changes | Native path | | Complete checkout session | Process payment and create order | Native path | | Redirect checkout | Redirect buyer to merchant checkout URL | Redirect path | | Order sync webhooks | Push order status updates to Google | Both paths |
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Why It Matters for Merchants
UCP agentic checkout turns the Google AI Mode and Gemini purchase surface into a direct revenue channel. Merchants who implement native checkout become purchasable within Google's AI interfaces without any buyer needing to leave the assistant. Merchants who implement redirect checkout gain discoverability and evaluation within those surfaces, with checkout completing on their own website — preserving their existing checkout experience while gaining AI surface presence.
The redirect checkout path in particular lowers the barrier to participation significantly. A merchant who is already UCP-enabled for discovery and search can add redirect checkout support without any API development, gaining an immediately purchasable presence in AI surfaces and collecting data on AI-referred traffic through their own checkout analytics before investing in the full native integration.
Order sync is also a competitive differentiator within this channel. Merchants who push order status updates reliably keep buyers informed within the AI interface throughout fulfilment, reducing post-purchase anxiety and support contacts. Merchants who do not sync order status leave the buyer with no visibility, which reduces satisfaction with the agentic purchase experience.
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FeedBridge Relevance
FeedBridge implements UCP Cart and Checkout capabilities as live features on the platform. The Cart API — create, update, get, and checkout multi-item sessions — is live, as is the Redirect Checkout capability (auto-enabled with privacy and ToS URLs). The UCP Dashboard Hub provides a compliance scorecard and capability checklist that includes cart and checkout capability status, so merchants can see at a glance which checkout path they have active and what steps remain to enable the other.
The API Playground in FeedBridge allows merchants to test Cart API responses in the dashboard before exposing them to AI agents — a useful verification step before seeking Google's integration approval. FeedBridge's Google Merchant Center CSV export supports the feed preparation step that precedes UCP checkout onboarding, ensuring that the product data layer that checkout depends on is structured and complete.
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Frequently Asked Questions
Q: Is redirect checkout sufficient for my products to be purchasable in Google AI Mode? A: Yes. Redirect checkout enables AI-assisted purchasing within Google AI Mode by directing the buyer to the merchant's own checkout page with pre-loaded cart contents. The buyer completes the checkout on the merchant's site. Native checkout provides a more seamless in-assistant experience but is not required to achieve a purchasable presence.
Q: Can I use Google Pay for native UCP checkout? A: Yes. Google's UCP implementation guide specifies Google Pay as the payment mechanism for native checkout on Google surfaces. Merchants must set up with Google Pay & Wallet Console, verify their PSP is in the list of processors that support Google Pay tokenisation, and note their Merchant ID for later integration steps.
Q: Does UCP cart support multi-item purchases? A: Yes. The UCP Cart API is explicitly designed for multi-item sessions — create, update, get, and checkout operations all operate on a full cart, not individual items. This makes it suitable for buyers who want to purchase multiple products in a single agentic transaction.
Q: Do I need to implement cart before native checkout? A: The Cart API and Checkout Session API are complementary but not strictly sequential in all implementations. A merchant implementing native checkout can reference item IDs directly in a checkout session creation request without a preceding Cart API session. However, the Cart API is the recommended path for agents handling complex or multi-step product selection flows before checkout.
Q: How do I handle a cart session that a buyer abandons? A: Cart sessions that are not checked out should be expired after a defined period. The UCP specification's lifecycle model includes session expiry. Abandoned cart sessions do not create orders and do not affect inventory — they are lightweight exploration sessions.
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Related Topics
Parent hub: UCP Checkout
Related concepts:
- What Is UCP?
- UCP Across the Full Shopping Journey
- UCP Capability Discovery Explained
- UCP Identity Linking Overview
Breadcrumb:
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Source Documentation
| Claim | Source | Source Class | Reference | |---|---|---|---| | UCP checkout: three core REST endpoints for create, update, complete; optional embedded checkout | Google UCP Guide | T1 – Official UCP Docs | https://developers.google.com/merchant/ucp/guides | | Integration must be approved by Google before going live on AI Mode and Gemini | Google UCP Guide | T1 – Official UCP Docs | https://developers.google.com/merchant/ucp/guides | | UCP supports guest checkout and account-linked checkout | Google UCP Guide | T1 – Official UCP Docs | https://developers.google.com/merchant/ucp/guides | | FeedBridge Cart API (create, update, get, checkout), redirect checkout auto-enabled | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | FeedBridge UCP Dashboard Hub, API Playground, Google Merchant Center CSV | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md |