Where things actually landed
OpenAI and Stripe announced the Agentic Commerce Protocol in September 2025 with Instant Checkout in ChatGPT. In March 2026 OpenAI retired Instant Checkout, saying it did not offer the flexibility they wanted. People were researching in ChatGPT and then buying where their card was already saved.
Google and Shopify launched the Universal Commerce Protocol in January 2026 with Walmart, Target, Etsy and Wayfair, and payment backing from Visa, Mastercard and Stripe. Universal Cart followed at I/O in May 2026. Separately, the Agent Payments Protocol was donated to the FIDO Alliance to become a standard.
The useful read is not which stack wins. It is that discovery is where agentic commerce is actually working today, and checkout is still settling. Publishing so that an agent can find, price and evaluate your products is the part that pays off now.
The one file you can publish today
The Universal Commerce Protocol manifest at /.well-known/ucp is the only agent checkout convention with public discovery. An agent fetches it and learns what your catalog and checkout support, without a partnership or an allow-list.
The Agentic Commerce Protocol has no equivalent. Participation is arranged with OpenAI and Stripe, and merchants expose private endpoints, so no scanner can verify it from outside. What can be verified are its prerequisites: a commerce platform that supports it, and a payment processor that has implemented it.
If you run Shopify, you may already be there
Every Shopify store has served a storefront MCP endpoint at /api/mcp by default since March 2026. That is a machine interface to your catalog that an agent can call without scraping anything. It is worth confirming yours answers, because a custom storefront can route around it.
For everyone else, the order that matters is: be readable, be parseable, then be transactable. A manifest pointing at a checkout an agent cannot reach is worth less than product pages it can actually understand.