---
title: What Is An AI agent?
description: An AI Agent is a system that completes a task by using a Large Language Model (LLM) to decide what steps to take and when the task is complete.
date: 2025-09-15
tags: [AI, Agents, Fundamentals]
status: Featured
---

There are many (disputed) definitions of what an AI Agent is, but here's mine: *An AI Agent is a system that completes a task by using a Large Language Model (LLM) to decide what steps to take and when it is complete.*

To put it more technically, to be an agent, the system has to **call an LLM**, which has **access to tools** it can optionally call and **runs in a loop** until the LLM deems the task as complete.

[This diagram](https://blog.langchain.com/what-is-an-agent/) from Harrison Chase (CEO of LangChain) clearly shows the boundaries between human-driven systems (steps 1 - 4) and agentic systems (steps 5 - 6) - using "cycles" as terminology here for loops.

<img
  src="/faqs/what-is-an-agent-harrison-chase.png"
  alt="Harrison Chase on agents"
  className="w-full max-w-[720px] rounded-lg shadow pt-4"
/>