Let me come back to the Agent Development Kit (ADK) for Java! We recently discussed the many ways to expand ADK agents with tools. But today, I want to explore the multi-agentic capabilities of ADK, by talking about sub-agent workflows.

In upcoming articles in this series, we’ll also talk about sequential, parallel, and loop flows.

The “divide and conquer” strategy

Think of building a complex application. You wouldn’t put all your logic in a single, monolithic class, would you? You’d break it down into smaller, specialized components. The sub-agent workflow applies this same “divide and conquer” principle to AI agents.

I recently gave a talk titled “AI Agents, the New Frontier for LLMs”. The session explored how we can move beyond simple request-response interactions with Large Language Models to build more sophisticated and autonomous systems.

If you’re already familiar with LLMs and Retrieval Augmented Generation (RAG), the next logical step is to understand and build AI agents.

What makes a system “agentic”?

An agent is more than just a clever prompt. It’s a system that uses an LLM as its core reasoning engine to operate autonomously. The key characteristics that make a system “agentic” include:

In a nutshell, the AI agent equation is the following:

AI Agent = LLM + Memory + Planning + Tool Use

AI agents are nothing without tools! And they are actually more than mere Large Language Model calls. They require some memory management to handle the context of the interactions (short term, long term, or contextual information like in the Retrieval Augmented Generation approach. Planning is important (with variations around the Chain-of-Thought prompting approach, and LLM with reasoning or thinking capabilities) for an agent to realize its tasks.

As I’m contributing to ADK (Agent Development Kit) for Java, and LangChain4j (the LLM orchestration framework) I interact with MCP (Model Context Protocol) servers and tools to further expand the capabilities of my LLMs.

Recently, I showed how to vibe-code an MCP server using Micronaut. You know I usually talk about Micronaut, but this time, I wanted to experiment with Quarkus, and in particular with its built-in support for implementing MCP servers.

Getting started with Quarkus’ MCP support

I created a brand new Quarkus project from IntelliJ IDEA, with its Quarkus template, and I added a couple key dependencies for JSON marshalling, but even more important, for the MCP support:

Recently on these pages, I’ve covered ADK (Agent Development Kit) for Java, launched at Google I/O 2025. I showed how to get started writing your first Java agent, and I shared a Github template that you can use to kick start your development.

But you also know that I’m a big fan of, and a contributor to the LangChain4j project, where I’ve worked on the Gemini support, embedding models, GCS document loaders, Imagen generation, etc.

With the unveiling of the Java version of Agent Development Kit (ADK) which lets you build AI agents in Java, I recently covered how to get started developing your first agent.

The installation and quickstart documentation also helps for the first steps, but I realized that it would be handy to provide a template project, to further accelarate your time-to-first-conversation with your Java agents! This led me to play with GitHub’s template project feature, which allows you to create a copy of the template project on your own account or organization. It comes with a ready-made project structure, a configured pom.xml file, and a first Java agent you can customize at will, and run from both the command-line or the ADK Dev UI.

At Google Cloud Next ‘25, last April, Google released Agent Development Kit (ADK) for Python, a flexible and modular framework for developing and deploying AI agents.

Now at Google I/O, a Java version of ADK has been made available! And I’m glad to have had the chance to participate in its launch, via code samples, documentation, and helping shape the API so it’s idiomatic for Java developers.

In this article, my goal is to give you the basis to get started with the ADK framework, in Java, using the Gemini model, and running your first Java agents locally.

In my previous article, I detailed how to build an AI-powered short story generation agent using Java, LangChain4j, Gemini, and Imagen 3, deployed on Cloud Run jobs.

This approach involved writing explicit Java code to orchestrate the entire workflow, defining each step programmatically. This follow-up article explores an alternative, declarative approach using Google Cloud Workflows.

I’ve written extensively on Workflows in the past, so for those AI agents that exhibit a very explicit plan and orchestration, I believe Workflows is also a great approach for such declarative AI agents.

This project demonstrates how to build a fully automated short story generator using Java, LangChain4j, Google Cloud’s Gemini and Imagen 3 models, and a serverless deployment on Cloud Run.

Every night at midnight UTC, a new story is created, complete with AI-generated illustrations, and published via Firebase Hosting. So if you want to read a new story every day, head over to:

→ short-ai-story.web.app ←

The code of this agent is available on Github. So don’t hesitate to check out the code: