How to Build an AI Agent
It’s Easier Than You Think
Everyone is talking about "AI Agents" like they’re some kind of alien technology, but here’s a secret: an agent is basically just 300 lines of code running in a loop. If you can understand a basic "if/then" statement, you can understand how the world’s most advanced AI tools actually work.
Here is the breakdown of how to go from someone who just uses ChatGPT to someone who builds the next big thing.
The "Loop" is the Brain
At its core, an agent is just a computer program that runs in a circle.
The Human asks a question.
The AI thinks about it (Inference).
The AI decides it needs to do something (like check the weather or write a file).
The code does that thing and tells the AI what happened.
The AI looks at the result and goes back to step 2.
You just keep throwing "tokens" (chunks of text) into the loop until the job is done. It’s not magic; it’s just a conversation that doesn't stop until the task is finished.
Know Your Models: Oracles vs. Squirrels
Not all AIs are built for the same job. Think of them like cars: you wouldn't take a minivan to a Formula 1 race.
Oracles: These are models like OpenAI’s o3. They are great at "thinking," summarizing huge books, or double-checking work. They are the professors.
Agentic Models (The Squirrels): These are models like Claude Sonnet. They are "agentic," meaning they act like a squirrel chasing a nut. They don't want to just talk; they want to do things. They are trained to look for "tools" they can use to solve a problem.
If you want to build an agent that actually does work, you want a "squirrel" model that is hungry to use tools.
The "Sticky Note" Problem (Context Window)
The AI’s memory is called a Context Window. Even though companies brag about how huge their memory is, it’s actually smaller than you think.
Imagine the AI has one small sticky note to do all its work on. If you start a chat about building a website, then ask it about your homework, then ask it to tell a joke, that sticky note gets covered in scribbles. Eventually, the AI gets "polluted" and starts making mistakes.
The Pro Tip: Hit "New Chat" all the time. Use one chat for one specific task. Keep that sticky note clean so the AI stays sharp.
Tools are Functions with Billboards
How does an AI "use" a tool? It’s simpler than it sounds. A tool is just a regular piece of code (a function) with a billboard on top.
The billboard is a text description that tells the AI: "Hey! If you need to know the temperature in Philadlephia, call this specific code." The AI reads the billboard, realizes it needs that info, and triggers the code. This is what people mean when they talk about MCP (Model Context Protocol)—it’s just a way to give the AI a library of billboards to choose from.
How to Build a Coding Agent
To turn an AI into a software engineer, you just need to give it four specific tools:
List Files: So it can see what’s in your folder.
Read File: So it can actually look at the code you wrote.
Bash/Terminal: So it can run commands (like "start the app").
Edit: So it can rewrite the code to fix bugs.
When you stack these four tools in that "loop" we talked about earlier, you have a coding agent. It looks at the files, identifies a bug, writes a fix, and runs a test to see if it worked. If the test fails, the loop starts over and it tries a different fix.
Why This Matters for You
The tech world is moving fast. We are entering an era where you can build an entire app while sitting in a boring Zoom call because the AI is doing the "heavy lifting" of typing out the code.
The goal isn't just to be a "consumer" of AI—someone who just asks it to write a poem. The goal is to be a producer. If you understand these 300 lines of code, you can automate your job, your chores, or your business. AI won't replace people, but people who know how to build these loops will have a massive head start.
Stop watching the tech happen—start building the loop.