START HERE · EDITORIAL INTRODUCTION
What does it mean
for an agent to pay?
A recommendation becomes a transaction when an agent can use authorized spending power to buy a service or product. Several layers make that possible.
Begin with a concrete task
A research agent needs access to a paid data source. Someone sets its spending rules; a compatible wallet or credential authorizes payment; the service verifies the payment and delivers the resource according to its flow.
This is a conceptual reading path, not a required message order for every protocol.
A few distinctions help
- Agent wallet
- Holds funds or supplies signing capability under an ownership and permission model.
- Payment protocol
- Defines how participants express payment requirements, authorization, and results. Different protocols cover different parts.
- Authorization
- Defines what the agent may do. A payment instruction alone is not evidence of permission.
- Facilitator
- An x402 role that verifies payment payloads and helps execute settlement. It can be hosted or implemented by a service itself.
- Stablecoin
- A payment asset. An asset such as USDC is a different concept from a protocol such as x402.
- Maturity
- A published specification, runnable example, and production integration are different evidence. None automatically establishes broad adoption.
Protocols do not all compete at the same layer
x402 focuses on paying for resources. AP2 focuses on verifiable authorization. UCP describes a wider commerce journey. AP2’s official examples include x402, and UCP documents AP2 support.
Read progress with the evidence attached
For each project, ask what is public, which parts can be tried, who controls funds, and which capabilities depend on partners. Our initial collection summarizes public information; it does not certify products or report hands-on payment tests.