[Feature] A2A Agent Card Registry - New Artifact Type

[carlesarnal]

Parent Epic

Part of #6991: AI Agent Registry

Description

Implement support for storing and serving A2A (Agent2Agent) Protocol Agent Cards as a new artifact type in Apicurio Registry.

Background

The A2A Protocol (developed by Google, now under Linux Foundation) enables AI agents to discover and communicate with each other. Agent Cards are JSON metadata documents that describe an agent's capabilities, similar to how OpenAPI describes REST APIs.

Apicurio can become the Agent Registry for multi-agent systems by storing and serving these Agent Cards.

Requirements

New Artifact Type: AGENT_CARD

1. Schema Definition

   • Define Agent Card JSON schema based on A2A specification
   • Validate Agent Cards on registration
   • Support schema evolution as A2A spec evolves

2. Agent Card Structure (per A2A spec)

   {
     "name": "MyAgent",
     "description": "Agent description",
     "version": "1.0.0",
     "url": "https://agent.example.com",
     "capabilities": [...],
     "skills": [...],
     "authentication": {...}
   }

3. Discovery Endpoints

   • /.well-known/agent.json - Standard A2A discovery endpoint
   • Support for proxying/serving individual agent cards
   • Search by capabilities and skills

4. Versioning & Compatibility

   • Version management for agent specifications
   • Compatibility rules for agent evolution
   • Breaking change detection

API Extensions

• New REST endpoints for agent-specific operations
• Agent capability search/filtering
• Bulk agent discovery for multi-agent orchestration

Acceptance Criteria

• AGENT_CARD artifact type is registered
• Agent Cards are validated against A2A schema
• Discovery endpoint serves agent cards
• Search by capabilities works
• UI displays agent cards appropriately

References

• A2A Protocol Specification
• Agent Card Schema
• A2A and MCP Relationship