A2A Agent Discovery

In the world of decentralized systems and smart agents, the Agent-2-Agent (A2A) Protocol plays a critical role in enabling communication and collaboration between autonomous agents. One of the foundational features of this protocol is Agent Discovery — the process by which agents identify and learn how to interact with other agents. This blog post explains what Agent Discovery is, why it matters, and how it works through different mechanisms.

What is Agent Discovery?

Agent Discovery is the process through which one agent finds and understands another agent’s existence and capabilities. It is an essential step before any two agents can communicate or collaborate. Without discovery, agents would operate in isolation, unable to leverage the skills or services of others in the ecosystem.

Agent Card

In A2A systems, every agent — particularly servers — must provide an Agent Card. This is a standardized JSON document that acts as the digital business card for the agent. The Agent Card includes:

• Identity: A unique identifier for the agent.
• Capabilities: What the agent can do or offer.
• Skills: Specific functions or features it supports.
• Service Endpoint URL: The network address where it can be reached.
• Authentication: Details on how other agents should authenticate before interacting.
• Interaction Instructions: Protocols or formats for proper communication.

Clients use the Agent Card to determine if an agent fits their needs and how to interact with it securely and effectively.

Agent Discovery Mechanisms

Direct Configuration

In Direct Configuration, the client is manually provided with all necessary information about the agent. This includes the agent’s endpoint, authentication method, and capabilities. It’s similar to setting up a device on a network using predefined settings. This method is simple but does not scale well when dealing with many agents or dynamic environments.

Well-Known URI

In this mechanism, agents publish their Agent Card at a predefined location on their server — usually under a standard path like /.well-known/agent-card.json. Clients attempting discovery will automatically look at this path to retrieve the agent’s information. This approach is more flexible than Direct Configuration and supports semi-automated discovery without relying on external registries.

Registries

Registries act like directories or yellow pages for agents. An agent can register its Agent Card with a centralized or decentralized registry. Clients can then query the registry to find agents that meet certain criteria, such as providing a specific skill or service. This method is highly scalable and dynamic, allowing agents to discover each other in large and evolving networks.