Protocols
A2A
A2A, the Agent2Agent protocol, is an open protocol for agents to discover one another and exchange messages. It is not a payment protocol. Payment enters an agent conversation through a separate standard such as AP2 or x402. This index does not treat A2A messages as volume.
Explanation
The A2A project publishes the protocol for interoperability between agents run by different vendors. A message can ask another agent to do work. Whether that work is paid, and on which rail, is outside A2A itself. Google's agentic-commerce repository specifies an x402 extension for agent flows, which is how an A2A-style conversation can require an x402 payment.
Keeping the layers apart matters for measurement. A conversation is not a settlement. If the payment then settles as a facilitator USDC transfer, it is x402 volume. Counting the A2A message as well would double-count the same purchase.
Live data
Related terms
Sources
- Agent2Agent protocol — A2A project
- AP2 x402 extension specification v0.2 — Google agentic commerce
- Agentic Payment Protocol specification, v0.2 — AP2