Top 10 Cursor Rules (.cursorrules) for Perfect AI Context

The `.cursorrules` file is the secret weapon of elite Vibe Coders. It's a simple text file that sits in your project root, but it has the power to transform how the AI understands and generates code for your project.

Think of it as a “permanent system prompt” that you never have to repeat. Once you set it up, every AI interaction in that project will follow your rules.

In this guide, we'll show you the Top 10 Cursor Rules that every project should have.

What is a `.cursorrules` File?

The `.cursorrules` file is a markdown file that Cursor reads automatically. It contains instructions for the AI about:
* Your coding style.
* Your preferred frameworks and libraries.
* Your team's conventions.
* Any project-specific context.

Location: Place it in the root directory of your project (same level as `package.json` or `README.md`).

The Top 10 Rules

Rule 1: Define Your Language and Framework

“`markdown
– You are an expert in TypeScript, React, and Next.js.
– Always use TypeScript for type safety.
“`

Why: This prevents the AI from suggesting JavaScript when you want TypeScript, or Vue when you're using React.

Rule 2: Specify Your Component Style

“`markdown
– Always use functional components with React hooks.
– Never use class components.
“`

Why: Consistency. If your codebase is all functional, you don't want the AI generating class components.

Rule 3: Set Your Styling Approach

“`markdown
– Use Tailwind CSS for all styling.
– Do not write custom CSS files.
– Use the `cn()` utility for conditional classes.
“`

Why: This ensures the AI doesn't mix Tailwind with inline styles or CSS modules.

Rule 4: Enforce Code Quality Standards

“`markdown
– Prefer `const` over `let`.
– Use `async/await` instead of `.then()` for promises.
– Add error handling to all async functions.
“`

Why: These are best practices that the AI might skip if not explicitly told.

Rule 5: Define Your File Structure

“`markdown
– Place all components in `src/components/`.
– Place all API routes in `src/app/api/`.
– Use kebab-case for file names (e.g., `user-profile.tsx`).
“`

Why: This prevents the AI from creating files in random locations or using inconsistent naming.

Rule 6: Set Documentation Standards

“`markdown
– Add JSDoc comments for all exported functions.
– Include @param and @returns tags.
– Keep comments concise and meaningful.
“`

Why: Good documentation is often skipped by AI. This forces it to be thorough.

Rule 7: Specify Your Testing Approach

“`markdown
– Write unit tests using Vitest.
– Place tests in `__tests__` folders next to the component.
– Aim for 80% code coverage.
“`

Why: If you don't specify, the AI might use Jest, or skip tests entirely.

Rule 8: Define Your API Patterns

“`markdown
– Use tRPC for type-safe API calls.
– All API responses should follow the format: { success: boolean, data: any, error?: string }.
– Use Zod for runtime validation.
“`

Why: API consistency is critical. This ensures every endpoint follows the same pattern.

Rule 9: Set Security Guidelines

“`markdown
– Never hardcode API keys or secrets.
– Always use environment variables for sensitive data.
– Sanitize all user inputs before database queries.
“`

Why: Security is non-negotiable. The AI needs explicit reminders to avoid common vulnerabilities.

Rule 10: Add Project-Specific Context

“`markdown
– This is a SaaS application for project management.
– The primary user is a small business owner.
– Prioritize simplicity and speed over advanced features.
“`

Why: This gives the AI the “why” behind the code, leading to better design decisions.

Example: A Complete `.cursorrules` File

Here's what a production-ready `.cursorrules` file looks like:

“`markdown

Project Context

– This is a Next.js 14 SaaS application for team collaboration.
– The target user is a remote team lead managing 5-10 people.

Tech Stack

– You are an expert in TypeScript, React, Next.js 14, Tailwind CSS, and Prisma.
– Always use TypeScript for type safety.
– Use the App Router (not Pages Router).

Code Style

– Use functional components with React hooks.
– Prefer `const` over `let`.
– Use `async/await` instead of `.then()`.
– Add error handling to all async functions.

Styling

– Use Tailwind CSS for all styling.
– Do not write custom CSS files.
– Use the `cn()` utility from `@/lib/utils` for conditional classes.

File Structure

– Components go in `src/components/`.
– API routes go in `src/app/api/`.
– Use kebab-case for file names.

Documentation

– Add JSDoc comments for all exported functions.
– Include @param and @returns tags.

Testing

– Write unit tests using Vitest.
– Place tests in `__tests__` folders.

API Patterns

– Use tRPC for type-safe API calls.
– All responses follow: { success: boolean, data: any, error?: string }.

Security

– Never hardcode secrets.
– Always use environment variables.
– Sanitize all user inputs.
“`

How to Test Your Rules

After creating your `.cursorrules` file, test it:
1. Open Cursor.
2. Press `Cmd+L` to open the AI chat.
3. Ask: “Create a new component for displaying user profiles.”
4. Check if the AI follows your rules (TypeScript, Tailwind, file location, etc.).

If it doesn't, refine your rules to be more explicit.

Conclusion

The `.cursorrules` file is the difference between an AI that “kind of” understands your project and an AI that feels like a senior developer on your team. Invest 30 minutes to set it up properly, and you'll save hours of refactoring.

At BYS Marketing, every project has a `.cursorrules` file. It's part of our onboarding checklist. It ensures that whether a human or an AI writes the code, it follows our standards.

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Want a team that codes with precision?
Contact BYS Marketing. We build with standards, not shortcuts.