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spec.capabilities ​

Declares which protocol-level capabilities the agent supports. streaming and pushNotifications are required so the schema makes the agent's contract explicit - a runtime should never need to guess whether streaming is on.

These are the A2A AgentCard capability flags - what a caller reads off the agent's card before connecting. See A2A & the Agent Card for what each flag means to a client.

yaml
spec:
  capabilities:
    streaming: true
    pushNotifications: true

streaming ​

  • Type: boolean
  • Required: yes

Whether the agent can stream incremental responses (typically token-by-token) back to the caller, instead of returning a single buffered result.

pushNotifications ​

  • Type: boolean
  • Required: yes

Whether the agent can push notifications about state changes - useful for long-running tasks where the caller subscribes and is informed when something happens.

extendedAgentCard ​

  • Type: boolean
  • Required: no

Whether the agent serves a richer, authenticated AgentCard via the A2A GetExtendedAgentCard method (GET /extendedAgentCard) once the caller is authenticated (A2A v1.0.1 AgentCapabilities.extendedAgentCard).

A note on defaults ​

The required flags have no defaults - streaming and pushNotifications must be explicitly true or false. This is intentional: a manifest that elides streaming would leave runtimes and clients unsure what to negotiate. Making the fields required forces the author to think about it. extendedAgentCard is optional and defaults to false - the richer card endpoint is opt-in.