Agent2Agent (A2A)

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The task is the centre

A2A puts a Task at the middle of the exchange: a server-generated identifier, a current status, artefacts, history and metadata. The caller can submit work, disconnect, reconnect and ask for the state.

That solves a genuine transport problem. A remote agent can request more input, report progress or return a file without exposing its own prompt, memory or tool implementation.

Completed is not accepted

The protocol's completed state means the remote implementation reached its terminal success state. It does not mean the parent agent accepted the file, the customer received what was promised, or a downstream record changed correctly.

That gap is the one to design for. A child task can complete while the parent discovers the schema is wrong, the evidence is stale or the customer needed something else. Acceptance is a separate record, owned by whoever is entitled to make it.

What sits beside the wire

Five questions stay outside the message: which person or organisation owns the objective; what this actor may do with the data and budget; what makes the returned work correct; whether this is a one-off request or a supplier contract; and who repairs a loss.

A signed message can show integrity. It cannot show that the sender had the right to commission the work.