UCP Interactive Protocol Support in Commerce Systems
> UCP interactive protocol support means implementing the Universal Commerce Protocol as a live REST-based API — rather than a static feed file — exposing a machine-readable manifest, catalog search and lookup endpoints, a cart API, and identity linking so that AI agents can discover, query, transact, and complete purchases directly against a merchant's commerce infrastructure in real time.
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What Is UCP Interactive Protocol Support?
The Universal Commerce Protocol defines a set of capabilities that allow AI agents and consumer-facing surfaces to interact with a merchant's commerce system programmatically — discovering what the merchant offers, searching and retrieving products, building and managing carts, and linking buyer identity to complete authenticated purchases. When a commerce system has "UCP interactive protocol support," it means this full capability set is live and accessible via standard REST API endpoints, not just declared in a feed document.
This is the key distinction between UCP interactive protocol support and a static feed format like the ACP JSON-LD feed. A static feed is a document — a file hosted at a URL, refreshed on a schedule, read by an AI platform in batch. It is valuable for product discovery but inherently delayed: the feed reflects the state of the catalog at the last refresh, not the current moment. The UCP interactive protocol is a live interface — an AI agent can query it at any time to get current product data, current availability, and current pricing, and can use it to create and complete a cart session within the same agent workflow.
For merchants targeting Google AI Mode and other UCP-enabled AI surfaces, interactive protocol support is the data infrastructure layer that enables real-time agentic commerce — the full workflow from query to cart to checkout, handled by an AI agent on the buyer's behalf, against live commerce data.
FeedBridge implements UCP interactive protocol support as a live capability — described in the platform as "Google AI Mode full REST-based" — exposing all five core UCP endpoints for merchants on the platform. FeedBridge's UCP Dashboard Hub provides a compliance scorecard and capability checklist, and the API Playground allows merchants to test Search, Lookup, and Cart responses in-dashboard before going live.
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The Five UCP Interactive Endpoints
UCP interactive protocol support consists of five functional endpoint areas, each serving a specific role in the agent commerce workflow:
1. Machine-Readable Manifest
Endpoint: `.well-known/ucp`
The manifest is the entry point for the entire UCP capability set. An AI agent or UCP-enabled surface that wants to interact with a merchant's commerce system first reads the manifest to discover what capabilities are available — which endpoints are live, what protocols are supported, and what the merchant's commerce infrastructure can do.
The manifest is hosted at the standardised path `/.well-known/ucp` on the merchant's domain (or on FeedBridge's hosted infrastructure for the merchant). It declares the merchant's UCP capabilities in a machine-readable format, following the UCP capability discovery specification. An agent reading the manifest knows immediately whether the merchant supports catalog search, catalog lookup, cart creation, identity linking, and redirect checkout — without needing prior knowledge of the merchant's specific implementation.
FeedBridge generates the machine-readable manifest as a live feature, conforming to the `.well-known/ucp` capability discovery standard.
2. Catalog Search API
Endpoint: POST `/ucp/catalog/search`
The Catalog Search API allows an AI agent to search the merchant's product catalog using free-text queries with filters and cursor-based pagination. When a buyer tells an AI assistant "show me noise-cancelling headphones under ₹15,000," the agent sends a structured search request to the Catalog Search API, which returns a filtered, ranked list of matching products from the merchant's live catalog.
Key capabilities of the Catalog Search API:
- Free-text search: Natural language or keyword queries against product data
- Filters: Category, price range, availability, brand, and other structured attributes
- Cursor pagination: Stateful pagination for browsing through large result sets without losing query context
3. Catalog Lookup API
Endpoint: POST `/ucp/catalog/lookup`
The Catalog Lookup API retrieves a specific product record by identifier. It supports two lookup methods: by `item_id` (the merchant's internal product identifier) and by barcodes — GTIN or MPN. This enables the precise, unambiguous product retrieval that high-intent agent workflows require.
The barcode-based lookup path is particularly significant for AI commerce: it allows an agent that knows a product's GTIN — from a buyer's existing purchase history, a scanned barcode, or a product database — to retrieve the merchant's specific offering for that product directly, without relying on title-matching. This is why GTIN and MPN presence in the product record matters for protocol compliance: products without these identifiers cannot be retrieved via the barcode lookup path.
FeedBridge's Catalog Lookup API supports both lookup modes as a live endpoint.
4. Cart API
Endpoint: POST `/ucp/cart`
The Cart API manages the transactional layer of the agent commerce workflow — creating, updating, retrieving, and checking out multi-item cart sessions. It is the bridge between product discovery and purchase completion, and it is the endpoint where the agentic commerce workflow transitions from "finding the right product" to "buying it."
Cart API operations include:
- Create cart session: Initiate a new cart with one or more products and quantities
- Update cart: Add, remove, or modify items in an existing session
- Get cart: Retrieve the current state of a cart session
- Checkout: Initiate the checkout flow for a cart session
FeedBridge's Cart API is live, supporting multi-item cart sessions with create, update, get, and checkout operations.
5. Identity Linking API
Endpoint: POST `/ucp/identity`
The Identity Linking API connects a buyer's agent-side identity to their merchant-side account — linking or unlinking buyer accounts using an OAuth 2.0 stub. This enables authenticated commerce experiences: a buyer who has an account with the merchant can link it to their AI agent profile, allowing the agent to access their saved addresses, payment methods, order history, and loyalty status when handling purchases on their behalf.
Without identity linking, the agent can discover and add products to a cart, but cannot complete authenticated checkout using the buyer's saved account data — the checkout falls back to a guest experience or a redirect flow. With identity linking, the agent can handle fully authenticated purchases within the agentic workflow.
FeedBridge implements Identity Linking as a live endpoint with OAuth 2.0 stub support.
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Redirect Checkout
In addition to the five API endpoints, UCP interactive protocol support includes Redirect Checkout — a fallback mechanism that is auto-enabled when a merchant implements UCP. Redirect Checkout handles cases where the full agentic checkout flow (via the Cart API) cannot be completed inline — for example, when the merchant's checkout requires additional verification steps, or when the buyer needs to complete authentication before purchase.
In a Redirect Checkout flow, the agent routes the buyer to the merchant's checkout page with the cart pre-populated, rather than completing checkout programmatically. The Redirect Checkout URL includes the merchant's privacy policy and Terms of Service URLs, ensuring buyers can access this information before completing the purchase.
FeedBridge auto-enables Redirect Checkout with privacy and ToS URLs as part of UCP implementation. This ensures that every UCP-enabled merchant has a functional checkout path even for edge cases where the Cart API checkout cannot complete inline.
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UCP Interactive Protocol vs ACP JSON-LD Feed
Understanding the relationship between UCP interactive protocol support and the ACP JSON-LD feed is important for merchants implementing both:
| Dimension | ACP JSON-LD Feed | UCP Interactive Protocol | |---|---|---| | Format | Static JSON-LD document | Live REST API endpoints | | Data freshness | Refreshed on schedule | Real-time, live data | | Primary channel | ChatGPT Shopping, ACP surfaces | Google AI Mode, UCP surfaces | | Product discovery | Feed polling / batch read | Catalog Search + Lookup APIs | | Cart and checkout | Not included in feed | Cart API + Redirect Checkout | | Identity | Not included in feed | Identity Linking API | | Capability discovery | Not applicable | `.well-known/ucp` manifest |
These two formats are complementary, not competing. A merchant implementing both ACP feed and UCP interactive protocol support achieves coverage across both major AI shopping protocol ecosystems — ACP-enabled surfaces (ChatGPT Shopping) and UCP-enabled surfaces (Google AI Mode). FeedBridge generates both from the same underlying product catalog, meaning the enrichment investment (intent tags, Q&A, personas, use cases) applies to both channels simultaneously.
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UCP Dashboard Hub and API Playground
FeedBridge's UCP Dashboard Hub is the compliance management centre for UCP interactive protocol support. It provides:
- Compliance scorecard: A dashboard view of the merchant's UCP compliance status across all five endpoint areas
- Capability checklist: A per-capability checklist showing which UCP features are live, which are partially implemented, and which are not yet enabled
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Why It Matters for Merchants
UCP interactive protocol support is the data infrastructure layer that makes real-time agentic commerce possible. A merchant with only a static feed can be discovered and evaluated by AI agents, but cannot support the full agent workflow — the agent cannot query live inventory, cannot create a cart session, and cannot complete purchase within the agent conversation. The buyer must be redirected to the merchant's website for each of these steps, breaking the agentic experience.
A merchant with full UCP interactive protocol support can support the complete agent journey: discovery via Catalog Search, product resolution via Catalog Lookup, cart management via Cart API, authenticated purchase via Identity Linking, and a fallback Redirect Checkout for edge cases. The buyer interacts entirely within their AI assistant; the merchant's commerce infrastructure handles the underlying operations invisibly.
For merchants targeting Google AI Mode specifically, UCP interactive protocol support is the primary technical requirement. Google AI Mode is a UCP-enabled surface that queries merchants via the UCP endpoint set — not via a static feed file. Merchants without UCP interactive support cannot participate in the real-time agent commerce workflow that Google AI Mode enables.
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FeedBridge Relevance
FeedBridge implements UCP interactive protocol support as a live capability, described as "Google AI Mode full REST-based" in the platform. All five endpoint areas are live: the machine-readable manifest at `.well-known/ucp`, the Catalog Search API (POST, free-text search with filters and cursor pagination), the Catalog Lookup API (POST, by `item_id` or barcodes GTIN/MPN), the Cart API (POST, create, update, get, and checkout multi-item sessions), and the Identity Linking API (POST, link/unlink buyer accounts, OAuth 2.0 stub). Redirect Checkout is auto-enabled with privacy and ToS URLs.
The UCP Dashboard Hub provides a compliance scorecard and capability checklist for monitoring UCP implementation status. The API Playground allows in-dashboard testing of Search, Lookup, and Cart responses. FeedBridge's AI Readiness Score includes UCP validation status within the Protocol Compliance dimension (30% of total score), ensuring that merchants can track and improve their UCP compliance alongside their ACP feed quality.
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Frequently Asked Questions
Q: Do I need to implement UCP and ACP, or just one? A: FeedBridge generates both the ACP JSON-LD feed and the UCP interactive protocol endpoints from the same product catalog. You do not need to choose one or the other — FeedBridge supports both simultaneously. ACP coverage reaches ChatGPT Shopping and ACP-enabled surfaces; UCP coverage reaches Google AI Mode and UCP-enabled surfaces. Implementing both maximises AI shopping channel coverage from a single catalog.
Q: What is cursor pagination in the Catalog Search API? A: Cursor pagination is a stateful pagination method where each page of results returns a cursor token that the agent includes in the next request to retrieve the following page. Unlike offset-based pagination (page 1, page 2, etc.), cursor pagination maintains consistency even when the underlying catalog changes between requests — a product added or removed between page reads does not cause items to be skipped or duplicated in the agent's result set.
Q: Is the `.well-known/ucp` manifest on my domain or on FeedBridge's infrastructure? A: FeedBridge hosts the UCP manifest as part of its hosted feed infrastructure. The manifest is accessible at the FeedBridge-hosted URL for each merchant brand, and FeedBridge manages the manifest content to reflect the merchant's live UCP capability status. Merchants who require the manifest to appear at their own domain path may need to implement a redirect or proxy from their domain to FeedBridge's hosted manifest URL.
Q: What is the OAuth 2.0 stub in the Identity Linking API? A: The OAuth 2.0 stub in FeedBridge's Identity Linking implementation provides the foundational OAuth 2.0 authentication structure required for buyer identity linking. "Stub" indicates that the implementation provides the authentication framework and endpoint structure — the mechanism through which a buyer's agent identity can be linked to their merchant account. Full production OAuth 2.0 integration with the merchant's specific account system is implemented on top of this foundation.
Q: Does UCP interactive protocol support replace my existing checkout flow? A: No. UCP interactive protocol support adds an agent-accessible commerce interface on top of your existing checkout infrastructure — it does not replace it. The Cart API creates cart sessions that route to your existing checkout process; Redirect Checkout sends the buyer to your existing checkout page with the cart pre-populated. Your existing checkout, payment processing, and order management systems continue to operate as before.
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Related Topics
Parent hub: Product Feeds and Commerce Data — Feed Formats
Related concepts:
- What Is the Universal Commerce Protocol?
- UCP Checkout Integration Basics
- ACP Feed JSON-LD Explained
- Hosted Feed URLs Explained
- FeedBridge UCP Support Overview
Breadcrumb:
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Source Documentation
| Claim | Source | Source Class | Reference | |---|---|---|---| | UCP Interactive Protocol: Google AI Mode full REST-based — live feature | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | Machine-Readable Manifest: `.well-known/ucp` capability discovery — live | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | Catalog Search API: POST, free-text search, filters, cursor pagination — live | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | Catalog Lookup API: POST, by item_id or barcodes GTIN/MPN — live | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | Cart API: POST, create, update, get, checkout multi-item sessions — live | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | Identity Linking API: POST, link/unlink buyer accounts, OAuth 2.0 stub — live | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | Redirect Checkout: auto-enabled with privacy/ToS URLs — live | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | UCP Dashboard Hub: compliance scorecard, capability checklist — live | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | API Playground: test Search, Lookup, Cart responses in-dashboard — live | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md | | Protocol Compliance 30%: ACP/UCP validation status — scoring dimension | FeedBridge Platform Capabilities April 2026 v2.0 | T1 – FeedBridge Internal | FeedBridge-Platform-Capabilities-April2026.md |