In A2A, work is organised as tasks. Each has an identifier and moves through a lifecycle.
Typical States
- Submitted: received but not started.
- Working: in progress.
- Input required: the remote agent needs more information from the client.
- Completed: finished successfully, with artifacts.
- Failed: couldn't be completed.
- Cancelled: stopped at the client's request.
- Other states, such as rejected or requiring authentication, may exist depending on the specification version.
Long-Running Work
Tasks can take seconds or days. Clients can:
- Wait for a response to simple requests.
- Stream updates as the task progresses.
- Receive push notifications to a webhook.
- Poll for status.
Multi-Turn Interaction
The "input required" state allows back-and-forth: a booking agent might ask which of several flights the user prefers, then continue.
Context
Related tasks can share a context identifier, grouping a conversation's worth of work.
Designing Remote Agents
Report meaningful status updates, fail clearly with reasons, and support cancellation so clients aren't left waiting.