What Is an A2A Agent Card?

An A2A agent card is a machine-readable document describing a single agent — its skills, its endpoints, and how to authenticate to it — commonly served at a well-known path so another agent can discover it. It answers "what can this agent do and how do I reach it," and composes with an organisation’s well-known agent document, which answers the broader "what does this organisation do and who is accountable."

Describes

One agent’s skills and endpoints

Found at

A well-known path

Card

The agent; org document: the organisation

Part of

A2A discovery

Agent-scoped, not organisation-scoped

A card is about an agent; the organisation-level well-known document is about the organisation and the human accountable for it. They compose: a card can be referenced from the organisation’s document, so a discovering agent moves from "who is this organisation" to "which agent do I talk to and how."

Related standards

A2A Agent CardA2A

Questions

How is an agent card different from a well-known agent document?

A card describes one agent’s skills; the organisation document describes the organisation’s capabilities and accountable human. One is agent-scoped, the other organisation-scoped, and they reference each other.

Who publishes an agent card?

The party that runs the agent, on their own domain, so authority and accountability stay with the domain owner.