Define an A2A agent
Unit 2 of 7 · Module 15: Discover Azure AI Agents with A2A
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Booths at a trade fair
At a trade fair, every booth has a sign listing what it offers, and a stack of business cards with the name, what the company does, and how to get in touch. That's how visitors find the right booth. A2A works the same way. It's an open standard for how agents share context, call on each other's abilities, and exchange information safely, even when they come from different vendors. Before an agent can join in, it has to say what it can do. It lists its skills, and publishes them on an agent card, so others can find it.
Why a shared protocol helps
A shared protocol brings a few advantages. Agents from different vendors and platforms can work together and share context, so you can automate across systems that were never connected. Each agent picks its own model, so a headline agent and a legal agent can each use the model that suits them best. And security is part of the protocol: an agent card says how callers must authenticate, like an API key or OAuth.
Skills and the card
A skill is one thing the agent can do, like suggest a title for a topic. Each skill has an ID and a name, a description, tags that help people search for it, example prompts, and the input and output formats it handles, such as plain text. The agent card is the business card that lists everything a caller needs. It gives the agent's name, description, and version, where to reach it, what protocol features it supports, like streaming or push notifications, the default input and output formats, its skills, and how callers authenticate. Keep it accurate: a wrong address or a missing skill is the quickest way to break discovery. Once the card is published, a routing agent can read the title agent's card and the outline agent's card, and plan the work: title first, then outline, then the finished answer.
Facts from Microsoft's documentation: Agent Framework: host agents with A2A; Foundry: A2A authentication (CC BY 4.0), rewritten in Loop's own words and examples. Narration, animation, and quiz by Loop. Microsoft, Azure, and Microsoft Foundry are trademarks of Microsoft. Loop is independent and not affiliated with or endorsed by Microsoft.