Agentic CommerceFour standards, three layers
Since late 2025 the major technology and payment players have published, one after another, the standards that let AI agents buy from merchants. They're often presented as rivals; in reality they sit at different levels of the same stack:
Commerce — discovery, cart, checkout, post-purchaseUCP · ACP
Payments — mandates, authorisation, auditabilityAP2
Connection — dialogue between AI models and systemsMCP
The protocol pages
- UCP — Universal Commerce Protocol (Google × Shopify, Jan 2026): the open standard covering the entire purchase journey, from catalog to after-sales.
- ACP — Agentic Commerce Protocol (OpenAI × Stripe, Sept 2025): buying inside a conversation — the protocol behind ChatGPT's Instant Checkout.
- MCP — Model Context Protocol (Anthropic, Nov 2024): the generic connection layer between AI models and merchant systems, which the others can build upon.
- AP2 — Agent Payments Protocol (Google × card networks, Sept 2025): securing agent-initiated payments through signed mandates.
For a cross-reading — overlaps, complementarities, and which combination fits your merchant profile — start with the detailed comparison.
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Comparison: UCP, ACP, MCP and AP2 side by side
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