Crate a2a_agents 

A2A Agents - Framework for building A2A Protocol agents

This crate provides a declarative, configuration-driven framework for building agents that implement the A2A Protocol v0.3.0.

Architecture

The crate is organized into three main layers:

• Core Framework (core) - Builder, configuration, and runtime
• Plugin System (traits) - Traits for extending agent functionality
• Utilities (utils) - Common helpers for agent development
• Example Agents (agents) - Reference implementations

Quick Start

use a2a_agents::core::AgentBuilder;

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    AgentBuilder::from_file("config.toml")?
        .with_handler(my_handler)
        .build_with_auto_storage()
        .await?
        .run()
        .await?;
    Ok(())
}

Core Framework

The core framework provides the essential building blocks:

• AgentBuilder - Fluent API for agent construction
• AgentConfig - TOML-based configuration
• AgentRuntime - Server lifecycle management

Plugin System

Implement the AgentPlugin trait to create agents that integrate seamlessly with the framework:

use a2a_agents::traits::{AgentPlugin, SkillDefinition};
use a2a_rs::port::AsyncMessageHandler;
use a2a_rs::domain::{A2AError, Message, Task};
use async_trait::async_trait;

#[derive(Clone)]
struct MyAgent;

impl AgentPlugin for MyAgent {
    fn name(&self) -> &str { "My Agent" }
    fn description(&self) -> &str { "An example agent" }
    fn skills(&self) -> Vec<SkillDefinition> { vec![] }
}

#[async_trait]
impl AsyncMessageHandler for MyAgent {
    async fn process_message(
        &self,
        _task_id: &str,
        _message: &Message,
        _session_id: Option<&str>,
    ) -> Result<Task, A2AError> {
        todo!()
    }
}

Features

• default - Includes reimbursement agent example and SQLx storage
• reimbursement-agent - Include reimbursement agent example
• sqlx - Enable SQLx-based task storage
• auth - Enable authentication features (JWT, OAuth2)

Re-exports

pub use core::AgentBuilder;

pub use core::AgentConfig;

pub use core::AgentRuntime;

pub use core::BuildError;

pub use core::ConfigError;

pub use core::RuntimeError;

pub use traits::AgentPlugin;

pub use traits::SkillDefinition;

pub use agents::reimbursement::ReimbursementHandler;

Modules

agents

Example agent implementations.

core

Core framework infrastructure for building A2A agents.

traits

Plugin traits for extending agent functionality.

utils

Utility modules for agent development.