Fetch capabilities (name, description, skills) of an A2A agent.

Send a message to an A2A agent and return its final text response.

The response ends with an [a2a task_id=... context_id=...] line. To continue the same conversation -- in particular to answer a [task input-required] question -- pass those ids back via the task_id / context_id arguments on the next call; omitting them starts a fresh task.

Long-running agent pipelines are expected: progress notifications are emitted while the task runs, so tune A2A_TIMEOUT_SECONDS rather than treating a slow response as a hang. If the call does time out after the task started, the error names the task_id -- the task keeps running server-side and get_a2a_task can retrieve its result.

Fetch the current state and result of a previously started A2A task.

Use this when send_a2a_message timed out or errored after the task had already started: the task keeps running server-side, and this retrieves its status and any output by the task_id from the error message or the [a2a ...] response footer.