AI Commerce Protocols

AI commerce protocols are the open standards that enable agentic commerce -- defining how AI agents discover products, access merchant data, complete checkouts, and manage post-purchase interactions on behalf of consumers.

Three protocols form the foundation of AI commerce infrastructure:

• ACP (Agentic Commerce Protocol) -- by Stripe and OpenAI (Sep 2025). Handles checkout and payment flows. Powers ChatGPT Instant Checkout.
• UCP (Universal Commerce Protocol) -- by Google and Shopify (Jan 2026). Covers the full commerce lifecycle from discovery through post-purchase. Powers Google AI Mode.
• MCP (Model Context Protocol) -- by Anthropic, now Linux Foundation (Nov 2024). The foundational data connectivity layer that lets AI agents access any external system.

Before these protocols, every AI shopping integration required custom development. A merchant wanting to sell through ChatGPT, Google AI, and Perplexity needed three separate integrations. Protocols standardize these interactions, reducing integration complexity from months to days.

The three protocols serve complementary functions at different layers of the commerce stack:

Data Layer (MCP): MCP lets AI agents access real-time product data, inventory, pricing, and order information from merchant systems. It is the foundation that both ACP and UCP can build upon.

Transaction Layer (ACP): ACP defines the checkout flow -- how an AI agent initiates a purchase, handles payment credentials through Stripe, and confirms an order. ACP is currently the protocol behind ChatGPT's Instant Checkout.

Orchestration Layer (UCP): UCP covers the entire commerce journey -- product discovery, browsing, cart management, checkout (via AP2), order tracking, returns, and customer service. UCP is designed to work with MCP for data access and can complement ACP for checkout.

The protocol landscape is new but moving fast. Practical steps for retailers:

1. Start with MCP: Make your product catalog accessible via MCP. This gives AI agents real-time access to your data regardless of which commerce protocol they use.
2. Enable ACP via Stripe: If you use Stripe for payments, enable ACP support to appear in ChatGPT Instant Checkout. Shopify merchants are auto-enrolled.
3. Prepare for UCP: Implement the /.well-known/ucp discovery endpoint as the specification stabilizes. Early adopters will have an advantage when Google AI Mode scales.
4. Use infrastructure platforms: Rather than building each integration separately, platforms like Paz.ai handle multi-protocol compliance through a single integration.