1000+ community rules

AI Agent Rules — What They Are & How to Use Them

AI agent rules are Markdown instruction files you commit to your project. Every time a coding agent like Cursor, Claude Code, or Copilot responds, it reads these files first — so it writes code that matches your stack, conventions, and patterns.

Without rules, AI assistants guess — using generic patterns from training data that rarely match your codebase. With a well-crafted rules file, the AI writes code that fits your project from the first suggestion.

Pick your stack and get a tailored rules file instantly:

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What a Rules File Looks Like

A plain Markdown file at the root of your project. Here's a real-world example for a Next.js SaaS:

.cursorrules

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# Project: My SaaS App

You are a senior TypeScript engineer on a Next.js 15 App Router SaaS.

## Critical Rules
- NEVER use `any` — use `unknown` with type guards
- ALWAYS use Server Components unless browser APIs needed
- NEVER use getServerSideProps — App Router only

## Tech Stack
- TypeScript 5.x (strict mode)
- Next.js 15 App Router
- Tailwind CSS v4 + shadcn/ui
- Drizzle ORM + PostgreSQL
- Vitest + Playwright

## Code Style
- Named exports only — no default exports
- Props typed as `{ComponentName}Props` interfaces
- Use `cn()` from `@/lib/utils` for Tailwind classes

This ~300-word file eliminates hundreds of AI correction cycles over the lifetime of a project. Generate one tailored to your stack →

Why It Matters

The Difference Rules Make

Without rules, AI writes generic code. With your rules, it matches your stack, conventions, and patterns.

Without Rules

Uses any — no type safety
Raw SQL query strings
useEffect for data fetching
Inline styles, no components

With Rules

Full TypeScript types
Type-safe ORM queries
React Query with caching
Project UI components

Without Rules

// AI generates generic code
 
function getUsers(db: any) {
  var result = db.query(
    "SELECT * FROM users"
  )
  return result
}
 
export default function UserList() {
  const [users, setUsers] = useState([])
  useEffect(() => {
    getUsers(db).then(setUsers)
  }, [])
  return users.map(u =>
    <div style={{padding: 16}}>
      {u.name}
    </div>
  )
}

Uses any — no type safety

Raw SQL query strings

useEffect for data fetching

Inline styles, no components

With Rules

// AI follows your project conventions
 
async function getUsers(): Promise<User[]> {
  return db.select().from(users).orderBy(users.name)
}
 
export function UserList() {
  const { data } = useQuery({
    queryKey: ["users"],
    queryFn: getUsers,
  })
  return (
    <Card>
      {data?.map(user =>
        <UserRow key={user.id} user={user} />
      )}
    </Card>
  )
}

Full TypeScript types

Type-safe ORM queries

React Query with caching

Project UI components

Coding Agent Rules — File by Tool

Each AI coding agent reads a different filename. Generate once in the builder, export to any format.

Cursor

docs ↗

.cursorrules

Most popular AI editor. Rules injected into every model call.

Claude Code

docs ↗

CLAUDE.md

Anthropic's terminal agent. Reads CLAUDE.md before every session.

GitHub Copilot

docs ↗

.github/copilot-instructions.md

Used by 1.8M+ devs. Applied to every Copilot Chat session.

Windsurf

docs ↗

.windsurfrules

Codeium's AI editor, direct Cursor competitor.

OpenAI Codex

docs ↗

AGENTS.md

OpenAI's agentic coding tool. Set up, constraints, and test commands.

Gemini CLI

GEMINI.md

Google's terminal coding agent powered by Gemini.

Using multiple AI tools?

Generate once in the builder and export to .cursorrules, CLAUDE.md, copilot-instructions.md, and more simultaneously.

Open Builder

Set Up Agent Rules in 5 Minutes

Pick your stack

Select your language, framework, and the AI tool you use. The builder finds the most relevant rules from 1000+ community examples.

Open Builder

Customize & export

Review the generated rules, tweak any section, then copy or download in the format your AI tool expects (.cursorrules, CLAUDE.md, etc.).

Browse Templates

Commit to Git

Add the file to your project root and commit it. Everyone on the team instantly benefits from consistent, convention-aware AI suggestions.

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Frequently Asked Questions

What are agent rules for AI coding assistants?

Agent rules are configuration files that tell AI coding assistants like Cursor, Claude Code, GitHub Copilot, and Windsurf how to write code for your specific project. They define your tech stack, coding conventions, architecture patterns, and preferences so the AI generates code that matches your style — instead of generic output. Think of them as a style guide that your AI pair programmer reads before writing any code.

What is a .cursorrules file?

A .cursorrules file is a configuration file placed at the root of your project that tells the Cursor AI editor how to generate code for that project. It can contain instructions about your tech stack, naming conventions, preferred libraries, architectural patterns, and coding style. Cursor reads this file automatically whenever it generates or edits code, ensuring consistent output that matches your project's standards.

What is CLAUDE.md and how do I use it?

CLAUDE.md is a Markdown file placed at the root of your project that provides instructions to Claude Code (Anthropic's CLI coding tool). Claude Code automatically reads this file when working on your project. You can include your tech stack, code conventions, project structure, and any specific instructions. It's also commonly used as a convention when working with Claude through other interfaces like the API or web.

What is copilot-instructions.md?

copilot-instructions.md is a file placed at .github/copilot-instructions.md that configures GitHub Copilot's behavior for your repository. It tells Copilot about your project's conventions, preferred patterns, and coding standards. GitHub Copilot reads this file automatically and applies the instructions when generating code suggestions, completions, and chat responses within VS Code or other supported editors.

How do I create agent rules for my project?

The fastest way is to use the Agent Rules Builder — select your language, framework, and AI coding assistant, and it generates a tailored rules file in seconds using 1000+ community-contributed rules. You can also create rules manually by adding a file like .cursorrules, CLAUDE.md, or .github/copilot-instructions.md to your project root and writing your conventions in Markdown. Our builder handles the formatting and exports to any agent format.

Is Agent Rules Builder free to use?

Yes, Agent Rules Builder is completely free. You can generate, customize, and export rules files for any supported AI coding assistant without any cost. There are no usage limits, no sign-up required, and no premium tiers. The tool is built on community rules and is designed to be accessible to all developers. Note: while the service is free to use, it is not open source.

View All 18 FAQs

Related Guides

What Are AI Coding Rules? Cursor Rules, CLAUDE.md, and Copilot Instructions Explained

A complete guide to AI coding rules — what .cursorrules, CLAUDE.md, and copilot-instructions.md are, why every developer needs them, and how to set them up in minutes.

Cursor Rules vs CLAUDE.md vs Copilot Instructions — Which to Use?

Cursor's .cursorrules, Claude's CLAUDE.md, and GitHub Copilot's copilot-instructions.md explained side-by-side — with a decision guide and multi-tool sync strategy.

How to Write AI Coding Rules for Cursor, Claude Code, and Copilot

Ten battle-tested principles for writing AI coding rules that actually work — with before/after examples, anti-patterns to avoid, and templates for .cursorrules, CLAUDE.md, and copilot-instructions.md.