Summary judgment: use UAI-1 when the durable exchange record, validation evidence, and public handoff boundary are the center of the decision. Use A2A source docs when you need agent-to-agent task coordination, discovery, or delegation behavior.
| Criterion | UAI-1 | A2A |
|---|---|---|
| Primary question | How can an exchange be validated, traced, and preserved across a public or organizational boundary? | How can agents discover one another, coordinate tasks, and delegate work across participating systems? |
| Evidence posture | Public message evidence, validation, provenance, integrity, and registry alignment are central. | Task coordination and agent capability exchange are central; consult the A2A docs for protocol-specific fields. |
| Best fit | Cross-boundary handoffs, release records, implementation evidence, and durable project memory. | Agent-to-agent workflows where task status, delegation, and interaction between agents matter. |
| Use together when | An A2A task or interaction produces an artifact, decision, or handoff that needs durable validation and source evidence. | |
Decision rule
If the problem is mostly about coordinating agents during work, read the A2A source first. If the problem is mostly about preserving a reviewable exchange after work crosses a boundary, read UAIX first. If both are true, document the live coordination separately from the durable evidence record.