Define an A2A agent

  • 5 minutes

The Agent-to-Agent (A2A) protocol is a standardized way for AI agents to communicate and collaborate with each other. It defines how agents can share context, invoke each other's capabilities, and exchange information securely. By adhering to the A2A protocol, agents from different vendors or platforms can work together seamlessly, enabling more complex and integrated AI solutions.

Before an A2A agent can participate in multi-agent workflows, it needs to explain what it can do. Agent Skills and how other agents or clients can discover those capabilities are exposed through an Agent Card.

Advantages of the Agent-to-Agent (A2A) protocol

The Agent-to-Agent (A2A) protocol offers several advantages for AI agent interactions:

  • Enhanced Collaboration:
    A2A enables agents from different vendors and platforms to share context and work together, allowing seamless automation across systems that are traditionally disconnected.

  • Flexible Model Selection:
    Each A2A agent can choose which large language model (LLM) to use for handling requests, enabling optimized or fine-tuned models per agent, unlike some MCP scenarios that rely on a single LLM connection.

  • Integrated Authentication:
    Authentication is built into the A2A protocol, providing a robust security framework for secure agent-to-agent communication.

Agent Skills

An Agent Skill describes a specific capability or function that the agent can perform. Think of it as a building block that communicates to clients or other agents what tasks the agent is designed to handle.

Key elements of an Agent Skill include:

  • ID: A unique identifier for the skill.
  • Name: A human-readable name describing the skill.
  • Description: A detailed explanation of what the skill does.
  • Tags: Keywords for categorization and easier discovery.
  • Examples: Sample prompts or use cases to illustrate the skill in action.
  • Input/Output Modes: Supported data formats or media types (for example, text, JSON).

When defining a skill for your agent, consider the tasks it should perform, how to describe them clearly, and how other agents or clients might use them. For example, a simple "Hello World" skill could return a basic greeting in text format, whereas a blog-writing skill might accept a topic and return a suggested title or outline.

Agent Card

The Agent Card is like a digital business card for your agent. It's a structured document that a routing agent or client can retrieve to discover your agent’s capabilities and how to interact with it.

Key elements of an Agent Card include:

  • Identity Information: Name, description, and version of the agent.
  • Endpoint URL: Where the agent’s A2A service can be accessed.
  • Capabilities: Supported A2A features such as streaming or push notifications.
  • Default Input/Output Modes: The primary media types the agent can handle.
  • Skills: A list of the agent’s skills that other agents can invoke.
  • Authentication Support: Indicates if the agent requires credentials for access.

When creating an Agent Card, ensure it accurately represents your agent’s skills and endpoints. This allows clients or routing agents to discover the agent, understand what it can do, and interact with it appropriately.

Putting it together

Once an agent defines its skills and publishes an Agent Card:

  • Other agents or clients can discover the agent automatically.
  • Requests can be routed to the agent’s appropriate skill.
  • Responses are returned in supported formats, enabling smooth collaboration across multiple agents.

For example, in a technical writer workflow, one agent could define skills for generating article titles, and another for creating outlines. The routing agent retrieves each agent’s card to discover these capabilities and orchestrates a workflow where a title generated by one agent feeds into the outline agent, producing a cohesive final response.