Independent editorial reference
Agent payment protocols, compared.
A maintained, machine-readable reference documenting AI-agent payment protocols and their real-world deployments — a living comparison matrix, per-protocol reference pages, a deployments registry, and a dated changelog. It is a reference, not a product.
Comparison, at a glance
See full comparisonHow these layers fit together
"Agent payments" spans several distinct layers that are easy to conflate. Separating them is the fastest way to read the matrix correctly — a communication layer neither settles value nor is "reversible."
Payment execution
Moves and settles value — the layer that actually pays. Example: x402 settling USDC on-chain.
Agent communication
Lets agents discover each other and coordinate tasks. Carries no money itself. Example: A2A.
Payment authorization
Captures consent and constraints so an agent can pay on a user's behalf. Example: AP2 mandates.
Wallet & custody
Account-abstraction and key-management primitives that hold funds and sign. Example: ERC-4337.