Crate a2a_client 

A2A Protocol Client

This crate provides a client for calling remote A2A (Agent-to-Agent) protocol compliant agents. It supports both streaming and non-streaming interactions over HTTP/HTTPS.

Features

• A2A v1 transport support over HTTP+JSON and JSON-RPC 2.0
• Non-streaming and streaming message support
• Task retrieval and listing
• Agent discovery via agent cards
• Authentication support (Bearer tokens)
• Error handling with detailed error types

Example

use a2a_client::A2AClient;
use a2a_types::{Message, Part, Role, SendMessageRequest, part};

// Create client from agent card URL
let client = A2AClient::from_card_url("https://agent.example.com")
    .await?
    .with_auth_token("your_api_key");

// Create message
let message = Message {
    message_id: "msg_123".to_string(),
    context_id: String::new(),
    task_id: String::new(),
    role: Role::User.into(),
    parts: vec![Part {
        content: Some(part::Content::Text("Hello!".to_string())),
        metadata: None,
        filename: String::new(),
        media_type: "text/plain".to_string(),
    }],
    metadata: None,
    extensions: Vec::new(),
    reference_task_ids: Vec::new(),
};

// Send message
let result = client
    .send_message(SendMessageRequest {
        tenant: String::new(),
        message: Some(message),
        configuration: None,
        metadata: None,
    })
    .await?;

Re-exports

pub use client::A2AClient;

pub use error::A2AError;

pub use error::A2AResult;

Modules

client

A2A Client for calling remote A2A agents

constants

Constants for the A2A client

error

Error types for A2A client operations

types

Re-export A2A protocol types so downstream crates can ensure they use the exact same type definitions as the client.