A2A (Agent-to-Agent) protocol support.

This module implements the A2A protocol for inter-agent communication. It enables LangChain Rust agents to discover, invoke, and communicate with other agents over HTTP using a JSON-RPC style protocol.

Architecture

• protocol: Core data types (AgentCard, A2ATask, A2ARequest, etc.)
• server: A2AServer - handler functions to expose an agent via A2A
• client: A2AClient - HTTP client to connect to remote A2A agents

Quick Start

Server (expose your agent)

use lc_a2a::{A2AServer, AgentCard};
use lc_chains::LLMChain;
use std::sync::Arc;

let chain = Arc::new(LLMChain::new(llm, "You are a helpful assistant"));
let server = A2AServer::new(chain)
    .with_card(AgentCard::new("my-agent", "A helpful agent", "http://localhost:8080"));

// In your HTTP handler (axum, actix, warp, etc.):
// GET /.well-known/agent.json -> server.get_agent_card()
// POST / -> server.handle_a2a_request(body).await

Client (call a remote agent)

use lc_a2a::{A2AClient, A2AMessage};

let client = A2AClient::new("http://localhost:8080".to_string());
let card = client.get_agent_card().await?;
let task = client.send_task(A2AMessage::user("hello")).await?;