a2aproject/a2a-java

Official Java SDK for the Agent2Agent (A2A) Protocol

What it solves

This library provides a standardized way for Java-based AI agents to communicate with each other. It implements the Agent2Agent (A2A) Protocol, allowing developers to build agentic applications that can interact regardless of the underlying transport layer or the specific agent implementation.

How it works

It is a multi-module Maven library that provides both client and server support. It enables agent communication over three primary transport mechanisms: JSON-RPC, gRPC, and REST (HTTP+JSON). The SDK allows a Java application to be run as an A2A server or to act as a client that can communicate with any other A2A-compliant agent.

Who it’s for

Java developers building agentic AI applications who need a standardized protocol for inter-agent communication and interoperability.

Highlights

  • Multi-transport support: Supports JSON-RPC, gRPC, and REST for flexible communication.
  • Reference implementations: Includes reference servers for JSON-RPC.
  • Enterprise Java integration: Community integrations available for Quarkus and Jakarta EE.
  • Extensible extras: Optional add-ons for OpenTelemetry, Kafka-based queue management, and Android HTTP clients.

Related

  • Project
    a2aproject/a2a-go

    A Go library for building and consuming AI‑style agents that follow the open Agent‑to‑Agent (A2A) protocol, with client/server APIs, support for gRPC/REST/JSON‑RPC, and extensible plug‑in points.

  • Project
    a2aproject/a2a-python

    A Python SDK for building agentic applications that follow the Agent2Agent (A2A) Protocol for standardized inter-agent communication.

  • Project
    a2aproject/a2a-js

    A TypeScript/JavaScript SDK for the Agent2Agent (A2A) Protocol, enabling the creation of interoperable AI agents and clients across multiple communication transports.

  • Project
    a2aproject/a2a-samples

    A collection of code samples and demonstrations for the Agent2Agent (A2A) protocol, designed to enable interoperability and communication between different AI agents.

  • Project
    LnYo-Cly/ai4j

    A Java AI Agentic SDK for JDK 8+ that provides unified access to multiple LLM platforms and built-in capabilities for agent orchestration, RAG, and durable long-term task management.