A2A describes how one agent can discover and communicate with another agent. The basic objects are easier to understand when they are treated as parts of a business task: a request, the messages exchanged while it is handled, and the artefacts produced along the way.

Tasks describe the work

A task represents a unit of work with an identity, state, input and expected result. It may be waiting, working, completed, failed, or interrupted. A clear task boundary makes it possible to retry, resume, inspect ownership, and explain what happened when an agent cannot finish.

Messages carry the conversation

Messages communicate instructions, progress, questions, results, and errors within the task. They should identify the intended role and preserve enough context for the receiving agent to act without guessing. Keep policy, identity, permissions, and business rules outside untrusted message text.

Artifacts are the useful outputs

An artifact is a produced object such as a report, structured record, file, draft, or decision request. Give it a type, owner, version, and access boundary. A link to agent cards and capability discovery explains how a partner advertises what it can do, while A2A and MCP separates agent collaboration from tool access.

• Define who may create, update, approve, and close a task.
• Make retries and duplicate delivery safe.
• Expose progress without leaking private context.
• Record the final artifact and the evidence behind it.

For production use, design the task lifecycle before choosing a protocol. The protocol can carry the exchange, but the business workflow still needs ownership, observability, timeouts, and a human route for exceptions.