a2a-ao 🤝

The first Rust implementation of the Agent-to-Agent (A2A) protocol — the open standard for agent interoperability, governed by the Linux Foundation.

What is A2A?

A2A enables AI agents to discover each other, delegate tasks, and collaborate — regardless of which framework or platform they were built on.

• Agent Cards — Self-describing metadata for agent discovery
• Tasks — Stateful units of work with full lifecycle management
• Streaming — Real-time updates via Server-Sent Events
• Push Notifications — Webhook-based async delivery
• Multi-turn — Extended dialogues with INPUT_REQUIRED / AUTH_REQUIRED states

Quick Start

use a2a_ao::{AgentCard, A2AClient, SendMessageRequest, MessagePart};

// Discover a remote agent
let card = AgentCard::discover("https://agent.example.com").await?;
println!("Found agent: {} ({})", card.name, card.description);

// Send a task to the agent
let client = A2AClient::new("https://agent.example.com");
let response = client
    .send_message(SendMessageRequest {
        message: Message::user(vec![
            MessagePart::text("Summarize this quarter's sales report"),
        ]),
        ..Default::default()
    })
    .await?;

// Track the task lifecycle
match response.task.state {
    TaskState::Completed => println!("Done: {:?}", response.task.artifacts),
    TaskState::Working => println!("Still working..."),
    TaskState::InputRequired => println!("Agent needs more info"),
    _ => {}
}

A2A + MCP: Complementary Protocols

Use A2A when agents need to collaborate. Use MCP when agents need tools and data.

License

MIT

Part of the AgentOven project.