Understanding A2A and Agent Cards

What is A2AJava?

A2AJava is a Java implementation of Google's Agent-to-Agent (A2A) protocol, designed to enable seamless communication and collaboration between AI agents. This framework provides a standardized way for AI agents to discover each other, share capabilities, and work together on complex tasks.

Agent Cards in A2AJava

What is an Agent Card?

An Agent Card is a digital representation of an AI agent's capabilities, metadata, and interaction endpoints. Think of it as a business card for AI agents - it contains all the information needed for other agents to understand what the agent can do and how to interact with it.

Automatic Card Generation

A2AJava uses Java reflection to automatically generate Agent Cards, making it easier to create and maintain agent implementations. Here's how it works:

1. Annotation Scanning:

   • The framework scans your codebase for classes annotated with @Agent
   • Methods annotated with @Action are identified as agent capabilities
   • Package scanning can be configured via action.packages.to.scan property

2. Metadata Extraction:
   

   @Agent(name = "MyCustomAgent")
   public class MyAgentImplementation {
       @Action(description = "Performs data analysis")
       public Response analyzeData(Request request) {
           // Implementation
       }
   }

• Agent name, description, and capabilities are extracted from annotations
• Method parameters and return types are analyzed to build the API specification

1. Dynamic Registration:
   • Cards are generated at runtime
   • Endpoints are automatically registered with the A2A server
   • Documentation is generated from Java annotations and method signatures

Customizing Agent Cards

There are three main ways to customize your agent cards:

1. Properties File Configuration

You can customize various aspects of your agent card through the application.properties file:

# Basic Card Information
a2a.card.name=My Custom Agent
a2a.card.description=A specialized agent for data processing
a2a.card.version=1.0.0

# Capabilities Configuration
a2a.card.capabilities.streaming=true
a2a.card.capabilities.pushNotifications=false
a2a.card.capabilities.stateTransitionHistory=true

# Provider Information
a2a.card.provider.organization=MyCompany
a2a.card.provider.url=https://mycompany.com

2. Runtime Modification

You can modify the card programmatically by extending A2ACardController:

@RestController
@RequestMapping("/a2a")
public class CustomAgentCardController extends A2ACardController {

    @GetMapping("/card")
    public ResponseEntity<AgentCard> getAgentCard() {
        AgentCard card = getCachedAgentCard();

        // Customize card at runtime
        card.setDescription("Dynamic description based on current state");
        card.getCapabilities().setStreaming(checkStreamingAvailability());

        return ResponseEntity.ok(card);
    }
}

3. Annotation-Based Customization

Use Java annotations to define card properties at the code level:

@Agent(
    name = "DataProcessingAgent",
    description = "Processes and analyzes data streams",
    version = "2.0"
)
@CardCapabilities(
    streaming = true,
    pushNotifications = true
)
public class DataProcessor {
    // Agent implementation
}

Best Practices

1. Consistent Naming: Use clear, descriptive names for your agents and actions

2. Documentation: Provide detailed descriptions in annotations and properties

3. Capability Management: Only expose capabilities that are fully implemented

4. Version Control: Maintain proper versioning in your agent cards

5. Dynamic Updates: Use runtime modification for state-dependent changes

6. Error Handling: Implement proper error responses in your card endpoints

Integration Example

Here's a complete example of a customized agent card implementation:

@RestController
@RequestMapping("/a2a")
public class CustomAgentCardController extends A2ACardController {

    @Autowired
    private AgentStateManager stateManager;

    @GetMapping("/card")
    public ResponseEntity<AgentCard> getAgentCard() {
        AgentCard card = getCachedAgentCard();

        // Dynamic customization based on state
        card.setDescription("Current state: " + stateManager.getCurrentState());
        card.getCapabilities().setStreaming(stateManager.isStreamingAvailable());

        // Add custom metadata
        card.addMetadata("lastUpdated", LocalDateTime.now().toString());
        card.addMetadata("activeConnections", stateManager.getConnectionCount());

        return ResponseEntity.ok(card);
    }
}

Conclusion

A2AJava's card generation system provides a flexible foundation for building AI agents that can seamlessly integrate with Google's A2A ecosystem. By combining automatic reflection-based generation with multiple customization options, you can create agents that are both powerful and adaptable to your specific needs.

Remember that while automatic card generation handles the heavy lifting, the ability to customize cards either through properties or at runtime gives you the flexibility to create dynamic, state-aware agents that can adapt to changing conditions and requirements.