A2A · Agent-to-Agent Protocol
How agents discover and delegate to other agents.
A2A is the Agent2Agent protocol — agents publish "Agent Cards" describing capabilities, and any other A2A agent can discover them and delegate tasks. JSON-RPC 2.0 over HTTP, with streaming support. A2A defines how agents talk; it does not define how agents pay.
The four things A2A actually delivers.
- Agents publish Agent Cards describing capabilities.
- Other agents discover and delegate via JSON-RPC 2.0 over HTTP.
- Streaming task progress + structured results.
- Stays explicitly silent on payment — that is intentional.
The flow, end to end.
Agent A asks
"Verify this insurance claim."
Discovers Agent B
Reads Agent B's Agent Card.
Delegates over A2A
Task delegated via JSON-RPC.
Agent B replies
Streams progress, returns result.
Your homework helper does not know everything, so it phones a friend — "hey, can you help my human with volcanoes?" The friend helps and sends the answer back. That is A2A.
Pay-per-delegation, governed
When Agent A pays Agent B for a task, xpay settles the call (via x402) and enforces Agent A's spending policies in the same step.
Monetize AI Agents →What A2A ships, what it does not, and what bridges the gap.
Open agent-to-agent communication, capability discovery, streaming.
No payment mechanism — when Agent A delegates, who pays Agent B?
Payment settlement on top of every A2A delegation, with the originating agent's spending policies enforced.
A2A compared.
A2A vs UCP
UCP is agent-to-merchant. A2A is agent-to-agent. An A2A delegate often turns around and calls UCP merchants under the hood.