How do AI coding agents actually work?
A chatbot can generate code. But it can't inspect your project or run your development workflow — you still copy the code, edit the files, run the commands, and verify it all yourself. Generating code is not the same as completing the task.
An AI coding agent is a model plus tools it can call. Instead of only producing an answer, it chooses an action, receives the result, and decides what to do next. That loop is what makes it an agent.
The part worth understanding — a tool call is not magic:
MODEL -> TOOL REQUEST -> AGENT RUNTIME -> TOOL EXECUTION -> TOOL RESULT -> MODEL
The model does not run anything itself. It emits a structured tool request. The agent runtime validates that request, executes it, and hands the result back. Then the model decides the next action, and round it goes again.
That distinction matters: the model has no automatic access to every file or command on your machine. It reaches only the tools its environment hands it, with the permissions you granted.
This 2-minute explainer shows the whole loop with a Ruby on Rails example — asking an agent to add payment validation, watching it read the model, edit the file, run RSpec, hit a failing test, read the error, fix it, and test again.
What you'll learn:
- What an AI coding agent is
- The difference between a chatbot and a coding agent
- How tool calling actually works, step by step
- How agents inspect and edit project files
- How they execute commands and run tests
- How they respond to a failing test
- Benefits, limitations, and security considerations
The loop:
REQUEST -> TOOL CALL -> TOOL RESULT -> REASON -> NEXT ACTION
Benefits: automates repetitive work, reads the project it's working in, runs tests and commands, speeds up debugging and exploration.
Trade-offs: it may misread the requirement, change the wrong thing, or run something unsafe. Tool access is a security surface, and it costs tokens and compute.
Which is why destructive actions should ask first. Permissions, sandboxing, and code review still matter — an agent is an assistant, not an authority.
Chapters:
00:00 — How AI Coding Agents Use Tools
00:10 — The Problem with Traditional Chatbots
00:25 — What Is an AI Coding Agent?
00:40 — How Tool Calling Works
01:00 — Practical Ruby on Rails Example
01:25 — Benefits and Trade-Offs
01:45 — The Takeaway
AI doesn't just write code. It can take action.
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