A2A-RS - Agent-to-Agent Protocol Implementation for Rust

A Rust implementation of the Agent-to-Agent (A2A) Protocol, providing both a robust framework library and practical agent examples. This project demonstrates production-ready agent communication with modern Rust practices and hexagonal architecture.

🎯 Quick Start - Try the Reimbursement Agent

See the A2A protocol in action with our reimbursement agent demo - a complete, self-contained example with both agent backend and interactive web frontend:

# Clone the repository
git clone https://github.com/emillindfors/a2a-rs.git
cd a2a-rs

# Run the complete demo (agent + web UI)
cd a2a-agents
cargo run --bin reimbursement_demo

# Open your browser to http://localhost:3000

The reimbursement demo showcases:

• 💬 Interactive web interface for submitting expenses
• 📋 Dynamic form generation for expense submissions
• ✅ Request validation and approval workflows
• 📊 Real-time task updates with streaming
• 🔄 Complete A2A protocol implementation (HTTP + WebSocket)
• 🌐 Production-ready architecture with frontend and backend

Try it out: Open http://localhost:3000 and submit an expense reimbursement request!

🏗️ Project Structure

This repository contains a complete A2A ecosystem:

📦 a2a-rs - Core Framework Library

The main library published on crates.io:

• 🚀 Complete A2A Protocol Implementation
• 🔄 HTTP & WebSocket Support with streaming
• 🏛️ Hexagonal Architecture with clean separation
• 🧩 Modular Features - use only what you need
• 📚 Comprehensive Documentation with examples

🤖 a2a-agents - Production Agent Examples

Real-world agent implementations demonstrating best practices:

• 💰 Reimbursement Agent - Handles expense requests with interactive workflows
• 🔧 Modern Architecture using the a2a-rs framework
• 📖 Full Documentation with setup guides

🔌 a2a-mcp - MCP Integration

Bridges A2A agents with the Model Context Protocol ecosystem:

• 🌉 Bidirectional Integration - A2A agents as MCP tools and vice versa
• 🔗 Protocol Translation between A2A and MCP formats
• 🛠️ Developer Tools for cross-protocol communication

💻 a2a-client - Web Interface

Browser-based client for interacting with A2A agents:

• 🌐 Web UI for agent communication
• 💬 Chat Interface with real-time updates
• 📱 Responsive Design for all devices

✨ Key Features

🎯 Framework Library (a2a-rs)

• Type-Safe Protocol - Rust's type system ensures protocol compliance
• Async-First Design - Built on Tokio with full async/await support
• Multiple Transports - HTTP, WebSocket with automatic fallback
• Streaming Support - Real-time task updates and progress tracking
• Authentication - JWT, OAuth2, OpenID Connect, API keys
• Storage Backends - SQLx integration for PostgreSQL, MySQL, SQLite
• Observability - Structured logging and tracing throughout

🤖 Agent Examples

• Production Ready - Complete implementations following best practices
• Interactive Workflows - Dynamic form generation and multi-step processes
• Business Logic Examples - Real use cases like expense reimbursement
• Framework Integration - Shows how to use a2a-rs effectively

🔧 Developer Experience

• Comprehensive Documentation - API docs, guides, and examples
• Working Examples - Copy-paste code that actually works
• Test Coverage - Integration tests and property-based testing
• Error Handling - Structured errors with helpful messages

🚀 Quick Integration

Add to your Cargo.toml:

[dependencies]
a2a-rs = "0.1.0"

# For HTTP client
a2a-rs = { version = "0.1.0", features = ["http-client"] }

# For HTTP server
a2a-rs = { version = "0.1.0", features = ["http-server"] }

# Everything
a2a-rs = { version = "0.1.0", features = ["full"] }

Simple Client Example

use a2a_rs::{HttpClient, Message};
use a2a_rs::port::AsyncA2AClient;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = HttpClient::new("http://localhost:3030".to_string());

    let message = Message::user_text("I need to submit a $50 lunch expense".to_string());
    let task = client.send_task_message("task-123", &message, None, None).await?;

    println!("Response: {:?}", task);
    Ok(())
}

Simple Server Example

use a2a_rs::{HttpServer, SimpleAgentInfo, DefaultRequestProcessor};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let server = HttpServer::new(
        DefaultRequestProcessor::new(),
        SimpleAgentInfo::new("my-agent".to_string(), "1.0.0".to_string()),
        "127.0.0.1:3030".to_string(),
    );

    server.start().await?;
    Ok(())
}

🎪 Advanced Examples

Streaming Client with WebSocket

use a2a_rs::{WebSocketClient, Message};
use a2a_rs::services::StreamItem;
use futures::StreamExt;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let client = WebSocketClient::new("ws://localhost:3030/ws".to_string());

    let message = Message::user_text("Process my reimbursement request".to_string());
    let mut stream = client.subscribe_to_task("task-456", &message, None, None).await?;

    while let Some(result) = stream.next().await {
        match result? {
            StreamItem::Task(task) => println!("Initial task: {:?}", task),
            StreamItem::StatusUpdate(update) => {
                println!("Status: {:?}", update);
                if update.final_ { break; }
            }
            StreamItem::ArtifactUpdate(artifact) => {
                println!("New artifact: {:?}", artifact);
            }
        }
    }

    Ok(())
}

🏛️ Architecture

The project follows hexagonal architecture principles:

┌─────────────────────────────────────────────────────────┐
│                   Application Layer                     │
│  ┌─────────────────┐    ┌─────────────────────────────┐ │
│  │  JSON-RPC       │    │     HTTP/WebSocket          │ │
│  │  Handlers       │    │     Transport               │ │
│  └─────────────────┘    └─────────────────────────────┘ │
└─────────────────┬───────────────────────┬───────────────┘
                  │                       │
┌─────────────────▼───────────────────────▼───────────────┐
│                     Port Layer                          │
│  ┌──────────────────┐    ┌──────────────────────────┐   │
│  │ MessageHandler   │    │  StreamingHandler       │   │
│  │ TaskManager      │    │  NotificationManager    │   │
│  │ Authenticator    │    │  RequestProcessor       │   │
│  └──────────────────┘    └──────────────────────────┘   │
└─────────────────┬───────────────────────┬───────────────┘
                  │                       │
┌─────────────────▼───────────────────────▼───────────────┐
│                    Domain Layer                         │
│  ┌──────────────┐ ┌──────────────┐ ┌─────────────────┐  │
│  │   Message    │ │     Task     │ │   AgentCard     │  │
│  │   Artifact   │ │ TaskStatus   │ │ Capabilities    │  │
│  │     Part     │ │   History    │ │    Skills       │  │
│  └──────────────┘ └──────────────┘ └─────────────────┘  │
└─────────────────────────────────────────────────────────┘

📚 Documentation

• Core Library Docs - Complete API documentation
• Reimbursement Agent Guide - Building production agents
• MCP Integration Guide - Cross-protocol communication
• Web Client Setup - Browser-based interfaces

🧪 Testing

# Test the core library
cd a2a-rs && cargo test --all-features

# Test agent examples
cd a2a-agents && cargo test

# Test MCP integration
cd a2a-mcp && cargo test

# Run integration tests
cargo test --workspace

🛣️ Roadmap

• Core Protocol - Complete A2A specification implementation
• Documentation - Comprehensive docs and examples
• Agent Examples - Production-ready reimbursement agent
• MCP Integration - Cross-protocol compatibility
• More Agent Types - Additional domain examples
• Performance Optimization - Benchmarking and improvements
• Advanced Auth - Enterprise authentication patterns

🤝 Contributing

We welcome contributions! Please see our Contributing Guide for details.

Development Setup

git clone https://github.com/emillindfors/a2a-rs.git
cd a2a-rs
cargo build --workspace
cargo test --workspace

📄 License

This project is licensed under the MIT License - see the LICENSE file for details.

🌟 Showcase

Built with a2a-rs? We'd love to feature your project! Open an issue to let us know.

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Ready to build intelligent agents? Start with our reimbursement agent example or dive into the core library documentation!