A Beginner's Guide to Multi-Agent Systems: How AI Agents Work Together

You've probably heard the term "AI agents" thrown around a lot lately. But recently, a new idea has been taking over engineering discussions: multi-agent systems . Not one AI doing everything: but a team of AIs, each with a specific job, collaborating to tackle complex problems. Here's a surprise: if you've ever used Claude Code to refactor a large codebase or fix a tricky bug, you've already seen a multi-agent system at work, you just might not have known it. If that sounds complicated, don't worry. By the end of this guide, you'll understand what multi-agent systems are, why they matter, and how to build a simple one yourself (no PhD required). First: What Even Is an "Agent"? Before we go multi, let's make sure we're clear on what a single agent is. A traditional LLM (like GPT or Claude) takes input and produces output — one shot, done. An agent goes further: it can reason , use tools , and take actions in a loop until a goal is completed. Think of it this way: LLM : "Here's a summar