Agentic commerce protocols explained: ACP, UCP, AP2 and x402, and what merchants should do now.
Four acronyms promise to let AI agents buy for people. One flagship launch has already been rolled back. Here is what each protocol does and where to spend your effort.
Agentic commerce is real and early. The protocols are useful to understand, and premature to bet the roadmap on.
The four protocols
| Protocol | Backed by | Does what | Status (Oct 2026) |
|---|---|---|---|
| ACP: Agentic Commerce Protocol | OpenAI, Stripe | Product feeds and agent-initiated checkout | Spec continues (beta); ChatGPT Instant Checkout reportedly ended March 2026 |
| UCP: Universal Commerce Protocol | Google, Shopify | Product discovery, capability negotiation, checkout | Manifest at /.well-known/ucp; checkout in early access |
| AP2: Agent Payments Protocol | Payment authorization with a signed user mandate | Used alongside UCP checkout | |
| x402 | Coinbase, Cloudflare (x402 Foundation) | HTTP 402 payments for resources, settled on-chain | Open source; used mainly for API and content payments |
What happened with ChatGPT checkout
ChatGPT Instant Checkout launched on 29 September 2025 on ACP, starting with US Etsy sellers. On 24 March 2026, reporting says OpenAI ended Instant Checkout, saying it wanted merchants to use their own checkout while it focused on product discovery. The ACP specification continued, and its role in ChatGPT is now mainly discovery through product feeds. Sources disagree on details, so check OpenAI's current documentation before planning around checkout.
What UCP asks of merchants
- An active Google Merchant Center account with eligible products.
- Products opted in through the product feed, with accurate pricing, availability, shipping and return policies.
- A JSON manifest at
/.well-known/ucpand checkout endpoints, or a platform such as Shopify that provides them. - Access to Google's UCP checkout is through an early access programme, initially in the US.
What to do now
- Get product data right. Feeds with correct prices, availability, identifiers and policies serve Google Shopping, ChatGPT discovery and any future protocol.
- Make prices readable on the page, matching your structured data. Check with our agent pricing checker.
- Make checkout agent-friendly: guest checkout, labelled fields, clear errors. Check forms with the agent form checker.
- Use your platform's path. If you are on Shopify or a similar platform, adopt its agentic commerce features rather than building protocol endpoints yourself.
- Watch, don't bet. Revisit quarterly. One flagship rollout has already been reversed.
Protocol details in this area change quickly and many write-ups are vendor blogs. We link primary specs where they exist; verify against them before building.
Questions people ask
What is the Agentic Commerce Protocol (ACP)?
An open standard from OpenAI and Stripe for product feeds and agent-initiated checkout. It powered ChatGPT Instant Checkout, which reporting says OpenAI ended in March 2026; the spec continues, mainly for product discovery.
What is UCP?
The Universal Commerce Protocol, co-developed by Google and Shopify, defines how AI agents discover products and check out with merchants. Merchants publish a manifest at /.well-known/ucp; Google's checkout access is in early access.
Do I need to implement these protocols?
Not yet for most merchants. Clean product feeds, readable pricing and an agent-friendly checkout matter more today, and platforms like Shopify provide protocol support.
Want this mapped onto your product?
See how our AAO work runs, or send your store link and a founder will reply personally.
