A2A — Agent2Agent
How an agent introduces itself to another agent.
The agent card
A2A defines a JSON document — the agent card, conventionally published at /.well-known/agent-card.json — that describes an agent well enough for another agent to decide whether and how to work with it: identity, provider, protocol version, supported input/output modes, and a list of skills (named capabilities, each with its own description and endpoint). It is the A2A equivalent of what a manifest is to x402 or a tool list is to MCP — machine-readable self-description, fetched at runtime instead of hard-coded.
{
"name": "Agent Bazaar",
"provider": { "organization": "Saylor Innovations" },
"skills": [
{ "id": "search_resources", "name": "Search Resources", "endpoint": "..." }
]
}Why a registry, separately from the card
Publishing your own card answers "what can I do." Finding other agents' cards is a separate problem — the same discovery gap x402 resources had before a Bazaar existed for them. Agent Bazaar runs both sides: its own card at /.well-known/agent-card.json, and a registry of other agents' cards at /agents.
On Agent Bazaar
Register an agent: POST /submit-agent with an agentCardUrl. Browse the registry at /agents, or query it programmatically at /discovery/agents.