Why it matters

Every integration requires the technical protocol details. Skimming past them causes broken implementations. Getting the shapes right up front avoids rework.

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The architecture

Core endpoints: /task/send (submit task), /task/get (poll status), /task/cancel, /task/subscribe (stream events).

Task lifecycle: submitted → working → completed / failed / canceled. Optional intermediate: input_required (agent needs more info).

A2A task lifecycleSend taskPOST payloadPoll or streamstate changesResultartifacts + statusServer can request additional input mid-task via input_required state; client responds
Task state machine.
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How it works end to end

Message shape: task ID, session ID, message parts (text, files, structured data). Extensible with new part types.

Artifacts: outputs. Can be intermediate (progress) or final. Multiple artifacts per task allowed.

Streaming: SSE-style events. Types include status updates, new artifacts, errors.