Most coverage of the Agentic Commerce Protocol repeats one of two lines: that ACP is “the ChatGPT buy button,” or that it died when OpenAI pulled back Instant Checkout in March 2026. Neither is right. ACP is a published specification, a contract for how an AI agent, a merchant and a payment provider exchange a product catalog, a cart, a checkout session and a payment credential. The first product built on it changed shape. The spec kept shipping. Here is how ACP works, what changed in ChatGPT, how it compares to Google’s Universal Commerce Protocol (UCP), and what to do now.
What the Agentic Commerce Protocol Is
The official GitHub repository describes ACP as “an interaction model and open standard for connecting buyers, their AI agents, and businesses to complete purchases.” It is open source under the Apache 2.0 license. OpenAI and Stripe are its Founding Maintainers, and the repo still labels the specification beta.
Governance is wider than the two founders: the repo’s governance document sets up a Technical Steering Committee, Meta holds one of its seats, and breaking changes need a written Standard Enhancement Proposal. The spec is versioned by date and has moved quickly:
- 2025-09-29: initial release, launched with ChatGPT Instant Checkout.
- 2025-12-12: fulfillment enhancements.
- 2026-01-16: capability negotiation.
- 2026-01-30: extensions, discounts and payment handlers.
- 2026-04-17: cart, feed, orders, authentication and MCP support (the latest stable version at the time of writing).
That last line matters. The 2026-04-17 version arrived after OpenAI changed its checkout plans, and it added product feeds to the protocol itself. Per the project site at agenticcommerce.dev, merchants can publish their checkout configuration through a traditional API or the Model Context Protocol.
The Four Moving Parts of ACP
Think of ACP as four separate contracts, any of which a merchant can adopt without the others:
- Product feed: a structured catalog the agent indexes so it can find and show your products with current price and availability.
- Agentic Checkout: a set of endpoints the merchant hosts so the agent can create, update, retrieve, complete or cancel a checkout session.
- Delegated Payment: a spec for payment providers that turns the buyer’s chosen payment method into a scoped, single-use token the merchant can charge.
- Order events: webhooks the merchant sends back so the agent can show the buyer what happened after purchase.
OpenAI’s commerce docs publish these as separate specs, which explains why ACP outlived its first product: discovery runs on the feed alone, and checkout is an opt-in layer on top.
How One ACP Purchase Flows
Pieced together from OpenAI’s key-concepts page and checkout spec, a purchase runs like this:
- The agent collects the buyer’s details, shipping address and payment choice inside the chat.
- The agent calls the merchant’s checkout endpoint (the
/checkout_sessionsresource) to create a session, then updates it as the buyer changes quantity or shipping. - The merchant validates the order, returns fulfillment options, calculates tax, runs its own fraud checks and charges the payment token.
- The merchant accepts or declines and returns that state. A session moves through
not_ready_for_payment,ready_for_payment, thencompletedorcanceled. - The merchant sends
order_createdandorder_updatedwebhooks through statuses such asconfirmed,shippedandfulfilled.
Every call carries an idempotency key, a signature, a timestamp and an API version, so a retry cannot double-charge a buyer. A trimmed create-session body looks like this (check the repo’s OpenAPI file before you build):
{
"items": [
{ "id": "sku_trail_shoe_42", "quantity": 1 }
],
"fulfillment_address": {
"name": "Alex Tan",
"line_one": "1 Market Street",
"city": "San Francisco",
"state": "CA",
"country": "US",
"postal_code": "94107"
}
}The key sentence in OpenAI’s docs: “OpenAI is not the merchant of record in the Agentic Commerce Protocol.” You keep the customer relationship, the payment processor, the tax liability and the refunds.
Shared Payment Tokens: Why the Agent Never Holds the Card
The payment layer is where Stripe’s role sits. Under the Delegated Payment spec, the agent prepares a one-time payment request with a maximum chargeable amount and an expiry, the payment provider returns a token, and the merchant charges that token. Stripe’s Shared Payment Token (SPT) was the first implementation.
Per Stripe’s agentic commerce docs, an SPT is “a scoped grant to use the customer’s payment method.” The agent sets usage limits on currency, maximum amount and expiry, and the agent can revoke it. A seller can charge it through Stripe or resolve it once into network credentials for a third-party processor. Stripe lists SPTs as available in the US, Canada and a list of European countries, and seller use is under preview terms.
Stripe is not the only provider: PayPal announced on 28 October 2025 that it would adopt ACP for payments in ChatGPT.
What Happened to Instant Checkout, and Why ACP Survived
Instant Checkout let ChatGPT users buy without leaving the chat. On 24 March 2026, as CNBC reported, OpenAI said “the initial version of Instant Checkout did not offer the level of flexibility that we aspire to provide,” and that it was “allowing merchants to use their own checkout experiences” while it focused on product discovery. Merchants can share product feeds and promotions, and those wanting deeper integration can build apps inside ChatGPT. CNBC named Target, Sephora and Nordstrom as early supporters of the new discovery experience.
So the question shifted from “can ChatGPT check out my product?” to “is my product in ChatGPT’s index at all?” OpenAI’s developer docs now open with “Start your ACP integration by sharing a structured product feed.” Onboarding is “currently available to approved partners,” and merchants apply at chatgpt.com/merchants. The step-by-step merchant side is covered in our ChatGPT Instant Checkout guide.
The Feed Is Where ACP Meets SEO
For a marketer, the feed spec is the most important page in the protocol, because it decides whether an agent can recommend you. OpenAI’s feed spec lists nine fields “required for a useful discovery feed”: item_id, title, description, url, brand, seller_name, image_url, availability and price.
Three flags control what a product can do. is_eligible_search defaults to true. is_eligible_checkout only works when search eligibility is on and checkout is enabled for your integration, and checkout also requires your privacy policy and terms URLs. The get-started guide recommends uploading a full snapshot at least once a day, and the spec says to update the feed when a sale starts or ends.
This is ordinary SEO hygiene in a new container. A stale price or vague title hurts a feed the same way it hurts a product page. The url field points to your product page, so whatever an agent cross-checks there needs to agree with the feed. Running a SEO Rocket real-crawler audit with JavaScript rendering shows what a fetcher actually receives on those URLs, including price and schema that only appear after scripts run. Our guide to product feeds for AI agents goes field by field.
ACP vs UCP: Side by Side
Google launched the Universal Commerce Protocol on 11 January 2026, saying it was co-developed with Shopify, Etsy, Wayfair, Target and Walmart and endorsed by more than 20 others, including Adyen, American Express and Best Buy. Here is how the two compare on what a merchant actually cares about:
| ACP | UCP | |
|---|---|---|
| Stewards | OpenAI and Stripe (Founding Maintainers), TSC with a Meta seat | Google and co-developers; Stripe sits on the UCP Tech Council |
| Main surface today | ChatGPT (discovery via feeds; checkout for approved partners) | Checkout button on eligible listings in AI Mode in Google Search and Gemini |
| Scope | Feed, cart, checkout, delegated payment, orders, authentication | Catalog, cart, checkout, identity linking (OAuth 2.0), orders, plus a draft lodging spec |
| Transports | REST or MCP | REST and JSON-RPC, with MCP, A2A and AP2 compatibility |
| Where your catalog comes from | A feed you send to OpenAI | Your existing Google Merchant Center feeds |
| Merchant of record | The merchant | The merchant (“you will remain the seller of record”) |
| License | Apache 2.0 | Apache 2.0 |
Google’s Merchant Center help page says UCP checkout applies to products eligible in the US, Canada and Australia, is “available for select merchants at this time,” and currently accepts cards stored in Google Wallet. For the full Google-side detail, see our UCP explainer.
Where ACP and UCP Really Differ
On the wire, the two are closer than the “protocol war” framing suggests: both model a checkout session the merchant controls, both keep the merchant as seller of record, both use scoped payment credentials, and both now speak MCP. The real difference is who sits in the middle.
With ACP, you are mainly courting OpenAI, and the work is your feed plus, if approved, checkout endpoints. With UCP, Google already has your catalog through Merchant Center, so the protocol adds a buy path on top of data you already maintain. That makes UCP the smaller step for a store already running Shopping ads, and ACP the bigger lever if ChatGPT is where your customers research.
The intermediaries are hedging. Stripe’s seller docs offer a Stripe-managed checkout through its Agentic Commerce Suite (available in the US, Canada and select European countries) and, separately, a path to “run your own Universal Commerce Protocol checkout” with the Stripe Payments handler. Shopify’s January 2026 announcement said merchants set up product data once in Agentic Storefronts and it surfaces in ChatGPT, Microsoft Copilot, Google AI Mode and Gemini. On a platform like that, the ACP vs UCP decision is largely made for you.
Which One Should Your Store Implement?
A decision rule that holds up better than “pick a side”:
- Shopify merchants: implement neither directly. Review Agentic Storefronts settings in Shopify Admin, check which AI channels are on, and spend your time on product data.
- Custom stack on Stripe: look at Agentic Commerce Suite first. Sharing a catalog feed with Stripe is far less work than hosting ACP checkout endpoints yourself.
- Merchant Center sellers in the US, Canada or Australia: UCP is the lower-effort path; check eligibility and submit Google’s interest form.
- Brands whose buyers research in ChatGPT: apply for ACP feed onboarding. Discovery is where the value sits since March 2026.
- Everyone else, including smaller stores outside these markets: do not build protocol endpoints yet. Fix product pages, schema and feed quality, which every agent reads regardless of protocol.
Do now: clean feeds, accurate prices, crawlable product pages. Watch: ACP checkout availability and UCP’s country list. Ignore: anyone selling a custom ACP build before your feed is approved.
What ACP Means for Product Page SEO
Agentic commerce raises the cost of inconsistency: an agent comparing your feed, your page and third-party reviews will notice when they disagree. Use the words buyers type as your feed titles, keep product schema in sync with the feed, and make sure AI crawlers are not blocked from product URLs. Our ChatGPT shopping optimization guide covers the recommendation side.
Then measure. SEO Rocket’s AI-visibility tracking shows whether AI answers mention your brand for the queries you care about, and its keyword research on real Ahrefs data tells you which product terms deserve a dedicated page in the first place. It is the same playbook proven across 1,000,000+ ranking pages, pointed at a new kind of reader.
FAQ
Is the Agentic Commerce Protocol only for ChatGPT?
No. ACP is an open, Apache 2.0 spec any agent platform can implement. ChatGPT was the first platform to implement it, so in practice most merchants meet ACP through OpenAI’s merchant program.
Did OpenAI stop supporting ACP?
No. OpenAI changed Instant Checkout in March 2026, but its developer docs still build merchant onboarding around ACP feeds, and the spec’s latest stable version is dated 2026-04-17.
Do I need Stripe to use ACP?
No. You keep your own payment processor. Stripe’s Shared Payment Token was the first delegated-payment implementation, PayPal has also adopted ACP, and Stripe tokens can be resolved for use with a third-party processor.
Should I support both ACP and UCP?
Eventually, and platforms like Shopify and Stripe make that cheap. Start with the surface your customers already use, and fix the product feed first.
The Bottom Line
The agentic commerce protocol is a contract, not a channel. OpenAI’s first checkout product stumbled, but the spec now covers feeds, carts, orders and MCP, and UCP solves the same problem from the Merchant Center side. Neither rewards stale product data. Get the feed right, keep product pages consistent with it, and track whether AI answers mention you; SEO Rocket handles the audit, keyword and AI-visibility steps in one chat.
