AI Coding Rules Builder

Why project context turns a generic AI into a teammate

Modern AI coding assistants — Cursor, GitHub Copilot, and the growing family of agent tools that read an AGENTS.md file — are extraordinarily capable, but out of the box they know nothing about your repository. They don't know that you use Eloquent instead of raw SQL, that controllers are PascalCase, that eval() is banned, or that every feature needs a test before it ships. Without that context they fall back on the statistical average of all the code they were trained on, which is why their first suggestions so often feel almost right but subtly off-house-style. A rules file fixes this. It is a small, plain-text document you commit to your repository that the assistant reads before every suggestion, giving it the same standing brief a new human teammate would get on their first day.

The three formats this tool produces all serve that same purpose with slightly different conventions. A .cursorrules file is the project-level instruction Cursor loads automatically from your repo root; it's plain sectioned text. copilot-instructions.md lives in .github/ and is the file GitHub Copilot reads to tailor its completions and chat to your repository; it's Markdown. AGENTS.md is an emerging open convention — a single Markdown file that any agentic coding tool can pick up to understand how to build, test, and contribute to your project. Whichever you choose, the content is the same idea: stack, style, conventions, preferred libraries, things to avoid, and testing requirements, written down once so you never have to repeat them in every prompt.

What makes a rules file genuinely effective

The most valuable section is almost always the guardrails — the "things to avoid" list. Telling an assistant what not to do ("never add a dependency without asking", "no inline styles", "do not disable type checks to make an error go away") is what keeps it from confidently steering your codebase somewhere you'll have to walk back later. Pair that with concrete style rules and naming conventions and you get suggestions that slot into existing files without a cleanup pass. Keep it specific and keep it tight: a rules file that tries to encode every preference under the sun becomes noise, and the assistant — like a person — gives most weight to a focused, well-organised brief. State the stack, the half-dozen rules that actually matter, the libraries you prefer, the handful of things you forbid, and how you expect code to be tested. That is usually enough to lift the quality of every completion and chat reply you get for the rest of the project.

Because the file is just text, it is also version-controlled like the rest of your code. When a convention changes, you edit one file, commit it, and every developer's assistant updates in lockstep — no shared chat history to sync, no per-person settings to chase. It works the same whether your team is on Cursor, Copilot, or an AGENTS.md-aware agent, and you can keep more than one format in the repo if different teammates use different tools. This builder assembles a clean, ready-to-commit version of whichever format you choose, entirely in your browser. Nothing you type is uploaded, stored, or sent to any model — fill the fields, pick a format, and copy or download the result straight into your project.