AgentCard

The AgentCard is a JSON document that describes an A2A agent's identity and capabilities.

Location

AgentCards must be served at:

{agent-base-url}/.well-known/agent-card.json

Agent Explorer automatically appends this path when you provide a base URL.

Required Fields

Field	Type	Description
`name`	string	Human-readable agent name
`url`	string	Agent's base URL
`version`	string	The agent's own version (e.g., `1.0.0`)
`protocolVersion`	string	A2A protocol version (e.g., `0.3.0`)
`capabilities`	object	Agent capabilities
`skills`	array	List of agent skills

Example AgentCard

{
  "name": "My Agent",
  "description": "An example A2A agent",
  "url": "https://example.com/agent",
  "version": "1.0.0",
  "protocolVersion": "0.3.0",
  "preferredTransport": "JSONRPC",
  "capabilities": {
    "streaming": true,
    "pushNotifications": false,
    "stateTransitionHistory": true
  },
  "defaultInputModes": ["text/plain"],
  "defaultOutputModes": ["text/plain"],
  "skills": [
    {
      "id": "general",
      "name": "General Assistant",
      "description": "Answers general questions",
      "tags": ["general"]
    }
  ]
}

Interface fields per protocol version

The two protocol versions describe endpoints differently — mixing them produces a non-conformant card:

0.3.0 — top-level url plus optional preferredTransport (defaults to JSONRPC) and additionalInterfaces ({ url, transport }). The authenticated extended card is advertised via the top-level supportsAuthenticatedExtendedCard flag.
1.0 — supportedInterfaces ({ url, protocolBinding, protocolVersion }) only; there is no top-level url or protocolVersion — endpoints and protocol versions live entirely in the interface list. Each interface's protocolVersion uses major.minor form (e.g. "1.0", "0.3"), per the spec. The extended card is advertised via capabilities.extendedAgentCard.

Capabilities

Capability	Description
`streaming`	Supports `message/stream` for SSE streaming
`pushNotifications`	Can push updates to a callback URL
`stateTransitionHistory`	Includes full state history in responses
`extendedAgentCard`	Supports the extended AgentCard format

Validation

Agent Explorer validates AgentCards and reports Errors (missing required fields, invalid types) and Warnings (missing recommended fields, potential issues).