AP2 Protocol: How Google Is Solving AI Agent Payments

The Problem AP2 Solves

Traditional payment systems assume a human is clicking 'buy' on a trusted surface. AI agents break this assumption. When an agent initiates a payment, critical questions arise: Did the user authorize this? Who is liable? AP2 provides a cryptographically verifiable chain of authorization from user intent to final settlement.

Announced in September 2025 with 60+ partners including Mastercard, PayPal, Amex, and Coinbase, AP2 was donated to the FIDO Alliance in 2026.

Core Concept: Mandates

AP2 uses three types of cryptographically signed mandates. Intent Mandate: the user's instruction defining scope. Cart Mandate: signed by the merchant to lock pricing and availability. Payment Mandate: contains transaction details and the user's cryptographic signature authorizing the specific payment. Every step is auditable.

Human-Not-Present payments (v0.2.0, April 2026) let users pre-authorize agents to make purchases autonomously within defined limits — perfect for limited-release tickets or routine restocking.

What Merchants Need to Do

AP2 readiness starts with UCP implementation since AP2 mandates reference UCP carts and products. Next, implement AP2 endpoint support on your checkout infrastructure. Finally, update your terms of service for agent-initiated purchases. For open-source harnesses, AP2 integration means adding mandate creation, cryptographic signing, and payment network submission to the agent's toolset.