# A2A Registry Architecture

## Project Overview

The A2A Registry is a production-ready agent discovery platform implementing **A2A Protocol v0.3.0** with comprehensive support for diverse agent ecosystems.

### Project Status

- **Version**: 0.1.1
- **Quality Gates**:
  - Type Checking: 0 errors (down from 118)
  - Linting: 0 errors (down from 44)
  - Test Coverage: 36/36 tests passing (100% pass rate)
  - Code Coverage: 28%

## High-Level Architecture

```mermaid
graph TB
    subgraph "Multi-Protocol Layer"
        JSONRPC[JSON-RPC 2.0]
        REST[REST API]
        GRAPHQL[GraphQL]
        GRPC[gRPC (Experimental)]
    end
    
    subgraph "Core Services"
        REG[Registration Service]
        DISC[Discovery Service]
        AUTH[Authentication Service]
    end
    
    subgraph "Storage Layer"
        MEM[In-Memory Store]
        DB[Database Backends]
    end
    
    JSONRPC --> REG
    REST --> REG
    GRAPHQL --> REG
    GRPC --> REG
    
    REG --> AUTH
    DISC --> AUTH
    
    AUTH --> MEM
    AUTH --> DB
```

## Core Architectural Components

### 1. Multi-Protocol Layer

Supports multiple transport protocols:
- **JSON-RPC 2.0** (Primary Transport)
- REST API
- GraphQL
- gRPC (Experimental)

### 2. Authentication & Security

- **Development Mode**: Open access
- **Production Mode**: 
  - JWT-based authentication
  - Role-Based Access Control (RBAC)
  - Configurable trust levels for agent registration

### 3. Extension System

- URI Allowlist configuration
- Trust level assignment
- Granular access control

### 4. Storage Backend

Flexible storage architecture supporting:
- In-Memory Storage (Development)
- Persistent Databases:
  - SQLite
  - PostgreSQL
  - MongoDB
  - Redis

## Existing Architecture Sections

[Rest of the existing document remains unchanged, preserving the detailed sections on:]

- Data Models
- Request/Response Flows
- Scalability Considerations
- Performance Characteristics
- Security Architecture
- Deployment Architecture
- Monitoring & Observability
- Configuration Management
- Next Steps

## Roadmap and Future Enhancements

1. Enhanced multi-region support
2. Advanced machine learning-based agent matching
3. More granular access controls
4. Expanded protocol support

## Best Practices

1. Use JWT for authentication in production
2. Implement agent health checks
3. Validate agent cards thoroughly
4. Use GraphQL for complex querying
5. Implement comprehensive error handling

## Compatibility

- **A2A Protocol**: v0.3.0
- **Python**: 3.9+
- **Supported Transports**:
  - JSON-RPC 2.0 (Primary)
  - REST
  - GraphQL
  - gRPC (Experimental)

## Acknowledgments

- [A2A Protocol Specification](https://a2a-protocol.org)
- [FastA2A](https://github.com/a2aproject/FastA2A)
- [FastAPI](https://fastapi.tiangolo.com/)
- [gRPC](https://grpc.io/)