Decoder
ACP, UCP, AP2, MCP — the agentic-commerce protocols, in plain English.
Four acronyms, a lot of confusion, and one reassuring truth: you don't implement any of them. Here's what each protocol is, who's behind it, and the only thing you actually have to do.
The short answer
ACP and UCP are how AI discovers and checks out your products. AP2 is how agents pay. MCP is the underlying agent-to-tools plumbing. The platforms implement all four — you just have to be ready for them.
The four protocols
What each one is — and what it means for you.
Backed by OpenAI (with Stripe)
The open standard OpenAI and Stripe published for agent checkout — how a merchant's products and checkout are exposed to an AI agent. It powered ChatGPT's Instant Checkout, which OpenAI wound down in March 2026; the protocol itself is still published.
For you: Today ChatGPT shoppers discover products in the chat and buy on your own site or inside your brand's ChatGPT app; Shopify's agentic storefronts in ChatGPT hand off to your checkout. What wins there is a complete, eligible catalog/feed. You don't hand-code ACP — your platform and feed do the work.
Backed by Shopify + Google (and partners)
The discovery + transaction standard for agentic storefronts — how AI agents find, understand and act on a store's catalog across surfaces like Google's AI shopping and Shopify's agentic storefronts.
For you: On Shopify this is largely automatic (agentic storefronts, agents.md, discovery). Your job is catalog quality and schema so the agent has something good to surface.
Backed by Google (and payment partners)
A standard for how an AI agent authorizes and settles a payment on a shopper's behalf — the 'can this agent actually pay' layer beneath agentic checkout.
For you: Payments plumbing handled by the platforms and processors. You care that your checkout is agent-compatible, not that you implement AP2 yourself.
Backed by Anthropic (widely adopted)
The general standard for connecting AI models to tools and data. Not commerce-specific, but it's how agents plug into systems — increasingly relevant for exposing store data and actions to AI.
For you: Mostly a developer/integration concern today. It matters when you want agents to read structured store data or trigger actions — an area to watch, not act on yet.
Emerging standards — details shift as the platforms iterate. We track the specs so you don't have to.
The only thing you actually have to do
Under every protocol, the lever is the same: a complete, machine-readable, schema-rich catalog; server-rendered facts; agent-compatible checkout; off-site authority; and measurement. Get those right and you're ready for whichever acronym wins.
FAQ
Questions we get a lot.
Still unsure? Ask an operator, not an SDR.
Book a 20-minute callWhat is the difference between ACP, UCP, AP2 and MCP?
ACP (OpenAI/Stripe) is the protocol for exposing products and checkout to ChatGPT; its in-chat Instant Checkout was wound down in March 2026, so ChatGPT shoppers now buy on the merchant's own site or app. UCP (Shopify/Google) is how agents discover and transact with a storefront across surfaces. AP2 (Google) is the payment-authorization layer for agents. MCP (Anthropic) is the general model-to-tools standard, not commerce-specific. In short: ACP and UCP are commerce discovery/checkout, AP2 is payments, MCP is the underlying agent-integration plumbing.
Do I need to implement these protocols myself?
Almost never. The platforms (Shopify, Google, OpenAI, payment processors) implement the protocols. Your job is to be ready for them: a complete, schema-rich, machine-readable catalog and an agent-compatible checkout. Getting the acronyms right matters far less than getting your store recommendable.
Which one matters most for a Shopify or Amazon merchant?
For Shopify, UCP-era agentic storefronts (your products surfacing in ChatGPT, Copilot and Gemini, handing off to your checkout) are where the near-term revenue is; for Amazon it's readiness for Alexa for Shopping (formerly Rufus) and COSMO (a separate track). In every case the lever is the same: catalog quality, schema, and cross-surface authority — which is exactly what an agentic-commerce readiness program delivers.
The protocols keep changing — how do I keep up?
You don't have to track every spec revision. Focus on the durable fundamentals (machine-readable catalog, complete schema, server-rendered facts, off-site authority, measurement); those pay off under every protocol. Run the free AI Shelf Check to see where you stand today.