ACP vs UCP: the two protocols that decide whether an AI agent can buy from you

If you sell anything online, two protocols now sit between your store and a growing share of your customers’ shopping. Both are open and both are backed by companies with a lot of users, so you’ll want to understand them well enough to ask your developer or platform the right question.

This post is written for business owners. Where the technical details matter for a decision, we’ll say so.

ACP: the Agentic Commerce Protocol

ACP came out of OpenAI and Stripe and launched alongside ChatGPT’s Instant Checkout on September 29, 2025. It’s the way ChatGPT reads a merchant’s catalog, presents products and hands off a purchase.

The basic idea is that the merchant publishes a product feed in a format that the agent can read and exposes a small set of endpoints that the agent uses to create a checkout, update it and complete it. Payment runs through a delegated token, which means the merchant stays the merchant of record and keeps its own payment processor. Stripe built the reference implementation, and in December 2025 it shipped an Agentic Commerce Suite so that merchants could sell through any ACP-compatible agent, not only ChatGPT. PayPal announced in October 2025 that it would run its own ACP server so its merchants could be reached without individual integrations.

Then in March 2026, OpenAI retired in-chat checkout and moved the purchase step back onto merchants’ own websites. As Search Engine Land reported in March, Walmart’s Daniel Danker said in-chat purchases converted at about a third the rate of sending shoppers to Walmart.com, even though ChatGPT was bringing Walmart roughly twice the rate of new customers that search did.

So ACP today is mostly about discovery and the handoff. ChatGPT reads your catalog through it and sends the shopper to you with the product already chosen. The checkout parts of the spec still exist and other agents may use them, but the largest consumer surface has pulled back from them.

If you’re on Shopify, ACP support is a platform feature, although only a few dozen Shopify merchants ever went live with in-chat checkout before OpenAI pulled it back. If you’re on another platform, ask whether it publishes an ACP-compatible feed.

UCP: the Universal Commerce Protocol

UCP is Google’s. It launched at NRF in January 2026, built with Shopify, Etsy, Wayfair, Target and Walmart and endorsed by twenty-odd others including Best Buy, Macy’s and The Home Depot. It’s designed to cover the full journey, from discovery through checkout and payment to post-purchase.

The most important piece for discoverability is the profile. A merchant publishes a machine-readable document at a well-known URL on its own domain (the /.well-known/ucp convention) that says what the business is and what it supports. An agent can fetch that in a single request and know, before it sends a customer, whether it can complete the transaction with you and how. Google’s stated reason for this design is to avoid every agent needing a custom integration with every merchant.

Gemini is built around UCP, including the Gemini Spark agent announced in May 2026. Google’s Agent Payments Protocol handles the money, and it lets the owner set a budget and a list of allowed merchants that the agent has to stay inside. Walmart’s experience is being integrated into the Gemini app directly.

Which one do you need?

Probably both, and the answer depends more on your platform than on your preference.

If you’re on Shopify, the platform is participating in both, and much of the work is already done or available as a setting. Check your store’s settings and Shopify’s own documentation for the current status.

If you’re on a large enterprise platform, ask your account team. Salesforce, commercetools and BigCommerce have announced support, and others may have since.

If you run a custom store, treat this as two integration projects. ACP is the smaller one, since it’s a product feed and a handful of endpoints, and Stripe’s tooling does a lot of the lifting if you use Stripe. UCP is more involved because it covers more of the journey, although the profile document on its own is cheap to publish. The profile describes what you support, but publishing it doesn’t by itself get you indexed, approved or recommended anywhere. That still depends on each platform’s onboarding and on your endpoints actually working.

If you’re a service business that takes bookings and doesn’t sell products online, neither protocol is your first priority. The equivalent for you is your booking system’s agent interface, which we cover in the agent-readiness checklist.

What to ask your developer or platform

These four questions will get you a straight answer:

• Do we publish a product feed that ChatGPT can read through ACP, and is it current?
• Do we publish a UCP profile at the well-known URL on our domain, and what does it say we support?
• When an agent sends a shopper to our site with a product chosen, does the checkout complete without an account, a popup or a CAPTCHA?
• Who is watching for changes to these specs, given that both have changed in important ways in the last year?

Most businesses skip that last question. The protocols were written in late 2025 and early 2026 and have already been revised, so something that worked in March may not work in October. Part of what FunnelPoint does is keep those connections current, so that you don’t have to follow every spec change yourself.

If you’d like us to check where your store stands on both, request a free assessment.