Live comparison of 8 agentic commerce protocols. Status, capabilities, trust architecture, and AXD analysis for UCP, ACP, Visa TAP, Mastercard VI, MPP, MCP, A2A..
| Dimension | Traditional UX | Agentic Experience Design (AXD) |
|---|---|---|
| Primary material | Attention and affordance | Trust and delegation |
| User state | Present, navigating | Absent, delegating |
| Design output | Screens and interfaces | Outcomes and constraints |
| Temporal model | Session-based | Relationship-based |
| Success metric | Task completion | Trust calibration |
UCP (Universal Commerce Protocol) and ACP (Agentic Commerce Protocol) are both open-source standards for AI agent shopping, but they differ fundamentally in scope and architecture. UCP, developed by Google and Shopify, covers the full commerce lifecycle — discovery, checkout, fulfilment, and returns — using a modular capability system and supporting multiple payment handlers per transaction. ACP, developed by OpenAI and Stripe, is checkout-focused, handling the transaction execution layer via St
Visa's Trusted Agent Protocol (TAP) and Mastercard's Verifiable Intent (VI) address different layers of the trust problem in agentic payments. TAP focuses on interaction trust — enabling merchants to recognise and verify approved AI agents at the web edge using HTTP Signatures (RFC 9421). VI focuses on authorisation trust — providing cryptographic proof that a human intended the agent to act, using a 3-layer SD-JWT credential model. TAP's primary verifier is the merchant; VI's primary verifier i
MCP (Model Context Protocol), created by Anthropic and now governed by the Linux Foundation, standardises how AI agents connect to external tools and APIs. While not a commerce protocol itself, MCP is the foundational infrastructure layer that enables agents to access commerce capabilities. An AI shopping agent might use MCP to connect to product databases, payment processors, and merchant APIs. MCP defines what an agent can do; commerce protocols like UCP and ACP define how it shops and transac
The proliferation of protocols reflects the multi-layered nature of agentic commerce. No single protocol can address all requirements: agent-to-tool communication (MCP), agent-to-agent coordination (A2A), product discovery and checkout (UCP/ACP), payment authorisation (Visa TAP, Mastercard VI), and payment execution (MPP). Each protocol addresses a specific layer of the stack. The AXD Institute tracks these protocols because their design decisions — particularly around trust, delegation, and ide
The answer depends on the organisation's role in the agentic commerce ecosystem. Merchants should prioritise UCP (for product discovery and checkout interoperability) and Visa TAP (for agent verification at the edge). Payment providers should implement MPP and Mastercard VI. Agent developers should adopt MCP (for tool access) and A2A (for multi-agent coordination). All organisations should monitor ACP's evolution as OpenAI's ecosystem remains significant despite the Instant Checkout pivot. The A
Live Protocol Comparison · Last Updated March 2026 Eight protocols are defining how AI agents discover, transact, pay, and communicate in the emerging agentic economy. This tracker compares their capabilities, No single protocol covers the full agentic commerce stack. The eight protocols tracked here operate at three distinct layers — Visa TAP and Mastercard VI represent two complementary approaches to the trust problem in agentic payments. TAP verifies the agent at the merchant edge; VI proves the human's intent at the issuer level. Together, they form the emerging trust infrastructure for Source: Fintech Wrap Up, Visa Perspectives, Mastercard specifications. March 2026. UCP and ACP represent two architecturally distinct approaches to agentic shopping. UCP models the full lifecycle; ACP focuses on the transaction. Both require merchant opt-in, which is why the coverage gap — addressed by universal checkout approaches — remains the central challenge. See Source: Rye.com, Google Developers, OpenAI. March 2026. Is Your Organisation Ready for Agentic Commerce? The protocol landscape is evolving rapidly. The AXD Readiness Assessment evaluates your organisation's preparedness across trust architecture, delegation design, agent observability, and recovery design.