PROTOCOL COMPARISON
AP2 vs. TAP vs. x402 for agent payments
AP2, Visa Trusted Agent Protocol and x402 solve different layers of agentic commerce. A payment boundary can normalize the facts needed for execution-time authority.
Published by MandateShield · Updated July 24, 2026SHORT ANSWER
Which protocol should an agent-payment team use?
Choose based on the commerce and payment rail you operate. AP2 emphasizes user mandates and payment evidence, TAP emphasizes trusted-agent identity and transaction context, and x402 enables HTTP-native machine payments. They can be complementary rather than mutually exclusive.
DimensionPrimary contributionBoundary implication
AP2User intent mandates and payment mandates for agent-led commerceVerify that final amount, merchant and execution still match the mandate
Visa TAPTrusted-agent identity, intent and transaction contextBind the acting agent and merchant context to the final purchase
x402HTTP-native payment negotiation and machine-to-machine settlementCheck authority before the client satisfies the payment requirement
Shared needMachine-readable purchase and identity evidenceFail closed on missing, expired, mismatched or replayed authority
MandateShield roleProtocol-neutral policy normalizationOne ALLOW, REVIEW or BLOCK contract immediately before execution
Primary contribution
Use this side when
- You are selecting the evidence and transport protocol for an agent flow.
- Multiple merchants or agents need interoperable identity and intent.
- Your architecture must follow a payment-network or HTTP-native rail.
Boundary implication
Use this side when
- You need one internal enforcement contract across protocols.
- Your payment code should not change whenever a protocol evolves.
- You need consistent reasons, replay control and evidence retention.
PRACTICAL ARCHITECTURE
How they work together
Use the protocol to carry native evidence and MandateShield to enforce normalized execution boundaries. It does not replace native signatures, payment processing or settlement.