How AI agents pay: the agentic payments stack

Layer 1: discovery and context (MCP)

Before an agent can buy anything it has to understand what is available. The Model Context Protocol, open-sourced by Anthropic on 25 November 2024 and donated to the Linux Foundation’s Agentic AI Foundation in December 2025, is the context layer: it connects agents to tools, catalogs and data through a standard interface. MCP carries no payments itself, but the commerce protocols increasingly advertise their checkout capability through it. ACP added MCP support in its 17 April 2026 spec, and Shopify exposed a public MCP endpoint for its agentic layer in June 2026.

Layer 2: checkout and commerce (ACP and UCP)

Once an agent knows what to buy, a commerce protocol completes the purchase. The Agentic Commerce Protocol (OpenAI and Stripe, 29 September 2025, Apache 2.0) is the checkout handshake that powers Instant Checkout in ChatGPT. The Universal Commerce Protocol (Google and Shopify, launched 11 January 2026, Apache 2.0) is broader, covering discovery, checkout and post-purchase across Google AI Mode and the Gemini app. They attach to different agent surfaces, which is why many merchants implement both. See the ACP vs UCP comparison.

Layer 3: authorization and consent (AP2)

Completing a cart is not the same as proving the shopper agreed to the spend. The Agent Payments Protocol (Google, 16 September 2025) is a payment-agnostic authorization framework: it carries verifiable proof that a user authorized an agent to pay a specific amount, across cards, bank transfers or stablecoins. AP2 is designed as an extension of MCP and A2A, and its crypto path is the A2A x402 extension. Read x402 vs AP2 for how settlement and authorization differ.

Layer 4: settlement rails (cards, x402, MPP)

The money then moves on a rail. On cards, the networks use tokenized credentials so the agent never touches raw card data: Mastercard Agent Pay uses Agentic Tokens, and Visa integrates tokenized Visa credentials into agent experiences (its June 2026 OpenAI partnership is one example). On stablecoins, x402 (Coinbase, 6 May 2025) settles on-chain through facilitators over the HTTP 402 status code, and MPP (Stripe and Tempo, 18 March 2026) settles stablecoins or fiat through Shared Payment Tokens for session-based and recurring agent billing. Compare the two crypto-capable rails in MPP vs x402.

Layer 5: trust and identity (TAP, Agentic Tokens)

The hardest problem is not moving money, it is knowing the agent is legitimate. Visa’s Trusted Agent Protocol (14 October 2025, with Cloudflare) lets a merchant cryptographically verify that an incoming agent is a sanctioned shopping agent using HTTP Message Signatures (RFC 9421). Mastercard’s Agentic Tokens carry the same trust on its rails. In June 2026 Visa added Agent Score and an Agentic Directory to Intelligent Commerce, and UK regulators began talking about know your agent checks. Trust is where the card networks are concentrating, and it is the layer a merchant cannot skip. The two card-network approaches are set out in Visa TAP vs Mastercard Agent Pay.

Putting it together

A single agentic purchase can touch all five layers: discover through MCP, check out through ACP or UCP, authorize through AP2, settle on a card or a stablecoin rail, and prove identity through TAP. For merchants, the practical takeaway is on how to accept payments from AI agents, and the full side-by-side is the standards comparison. Every date here is tracked on the changelog.