Tired of Claude's Sloppy Code? A Single Config File Increases Accuracy by 10%

Introduction

Have you ever experienced this? You open Claude Code full of hope, only to find it completely confused about your project. You’re building with React, but it generates Vue code. Your tech stack docs clearly state TypeScript, yet it outputs pure JavaScript everywhere.

I hit this exact problem the first time I used Claude Code. Working on a Node.js backend project, Claude decided to rewrite my Koa-based code with Express, breaking the entire middleware system. That’s when I realized: no matter how smart AI is, it needs you to tell it the “rules of the game.”

The solution is simpler than you might think—a configuration file called CLAUDE.md. Think of it as a “project manual” for AI, telling it about your tech stack, coding standards, and workflows. According to Anthropic’s testing, a well-configured CLAUDE.md can improve AI coding accuracy by 5-10% while reducing irrelevant suggestions.

Today I want to share 7 practical tips to help you write truly effective CLAUDE.md files. These are all lessons I learned the hard way, each with ready-to-use example code.

What Exactly is CLAUDE.md

Simply put, CLAUDE.md is a Markdown file placed in your project root to guide Claude Code in understanding your project. It’s similar to .editorconfig or README.md, but more specific—telling AI how to help you write code.

The mechanism is straightforward: When you use Claude Code in your project, it automatically reads this file. While the official docs say it loads automatically, community experience suggests it’s best to explicitly remind it with the /init command to ensure AI has “understood” your configuration. The file content is loaded into AI’s context memory, influencing all subsequent code generation and suggestions.

Here’s a key feature—Claude Code supports hierarchical configuration:

project-root/
├── CLAUDE.md              # Global config (entire project)
├── frontend/
│   └── .claude/
│       └── CLAUDE.md     # Frontend-specific config
└── backend/
    └── .claude/
        └── CLAUDE.md     # Backend-specific config

This means you can define general standards in the root directory, then override specific rules in submodules. For example, if frontend uses React and backend uses Node.js, each can maintain its own configuration.

Four Core Principles

Before writing CLAUDE.md, remember these four principles. I didn’t pay attention to these at first, wrote a 300+ line “epic” configuration file, and Claude’s performance actually got worse.

1. Conciseness: The 100-Line Rule

To be honest, I learned this lesson the hard way. CLAUDE.md is not a README—it doesn’t need lengthy explanations.

Why be concise? From a technical standpoint, while Claude has a large context window, CLAUDE.md consumes your token quota. The longer the file, the fewer tokens available for actual code analysis. According to Arize AI research, configuration files under 100 lines work best.

❌ Bad Example (verbose and repetitive):

# Project Introduction
This is a React-based frontend project. We use React to build user interfaces.
React is a JavaScript library developed by Facebook... (200 words about React omitted)

# Tech Stack
Our tech stack includes the following:
- React - This is our UI framework, version 18.2...
- TypeScript - We use it for type checking...

✅ Good Example (concise and direct):

# Tech Stack
- React 18.2 (Hooks preferred, avoid Class components)
- TypeScript (strict mode)
- TailwindCSS (utilities-first)

# Coding Standards
- Function components + custom Hooks
- Props destructuring
- Prefer const, avoid let

See the difference? The second version conveys the same or more useful information with just 60 characters.

2. Specificity: Be Clear, Not Vague

This principle sounds simple but is easy to violate.

❌ Bad Example (vague):

# Code Style
- Keep code concise
- Follow best practices
- Pay attention to performance

This is essentially useless. What does “concise” mean? What are “best practices”? AI has no way to execute this.

✅ Good Example (specific and actionable):

# Code Style
- Single function max 50 lines, split if exceeded
- API calls MUST include error handling and loading states
- List rendering MUST add key prop, use ID not index
- Avoid nested ternaries, use if/else or early return

Now AI knows what to do. Each rule is clear and verifiable.

3. Iterability: Don’t Be Afraid to Update

I’ve seen developers write CLAUDE.md at project start, then never touch it for six months. The project migrated from Vue 2 to Vue 3, but the config still says “use Options API.”

Quick updates with # key: This is my favorite trick. In Claude Code, press # to quickly reference and edit CLAUDE.md. When you notice AI behavior doesn’t match expectations, update the config immediately—don’t delay.

Real scenario: Last week on a project, Claude kept generating code with axios, but our team standardized on fetch + custom wrapper. I immediately pressed # and added a line to CLAUDE.md:

# HTTP Requests
- Use `src/utils/request.ts` fetch wrapper uniformly
- Do NOT use axios or raw fetch directly

After saving, Claude never made that mistake again.

4. Team Sharing: Include in Version Control

Many people overlook this. CLAUDE.md must be committed to Git, as important as .gitignore.

Why? Because your configuration represents team coding consensus. If everyone has different local versions of CLAUDE.md, AI generates code in one style for Zhang San and completely different for Li Si—chaos ensues.

# Don't ignore CLAUDE.md in .gitignore
# ❌ Wrong approach
*.md

# ✅ Correct approach
*.md
!CLAUDE.md
!README.md

Also review CLAUDE.md changes during Code Review. If someone modifies the config, the whole team should know.

5 Essential Content Modules

This is my minimum viable configuration. Without these modules, CLAUDE.md is basically useless.

1. Tech Stack Declaration

Must explicitly list frameworks, libraries, and versions. This is fundamental.

# Tech Stack
**Frontend**
- Next.js 14 (App Router)
- React 18 (Server Components preferred)
- TypeScript 5.2
- Tailwind CSS 3.4

**Backend**
- Node.js 20 LTS
- Express 4.18
- Prisma ORM
- PostgreSQL 15

Notice I included version numbers. Without versions, Claude might generate code with outdated APIs. For example, Next.js 13 and 14 routing are completely different—not specifying versions is dangerous.

2. Project Structure

Tell AI how your files are organized so it can place code in the right location.

# Project Structure
src/
├── app/              # Next.js page routes
├── components/       # Reusable UI components
│   ├── ui/          # Base components (Button, Input)
│   └── features/    # Business components (UserCard, OrderList)
├── lib/             # Utility functions and hooks
├── services/        # API call layer
└── types/           # TypeScript type definitions

# File Naming
- Components: PascalCase (UserProfile.tsx)
- Utils: camelCase (formatDate.ts)
- Constants: UPPER_SNAKE_CASE (API_BASE_URL)

With this, Claude knows a new user card component should go in components/features/UserCard.tsx, not just anywhere.

3. Common Commands

This section is often overlooked but super useful.

# Development Commands
npm run dev          # Start dev server (localhost:3000)
npm run build        # Production build
npm run test         # Run Jest tests
npm run lint         # ESLint check
npm run type-check   # TypeScript type check

# Database
npx prisma studio    # Open database GUI
npx prisma migrate dev  # Run database migration

Why include this? Because Claude sometimes needs to validate code or run tests—telling it the correct commands avoids many issues.

4. Code Style Guidelines

This is the centerpiece. Must be specific enough.

# Coding Standards

## React Components
- Use function components + Hooks, NO Class components
- Props type definition above component, use interface not type
- Component internal order: Props definition → Component function → Export

## State Management
- Local state: useState/useReducer
- Server state: TanStack Query
- Global state: Zustand (avoid Context)

## Error Handling
- API calls MUST use try-catch
- User-facing errors use toast notifications
- Dev environment: console.error, Production: report to Sentry

5. Workflow and Restrictions

Tell AI what it can and cannot do.

# Workflow
- New features: Write type definitions → Write component → Write tests
- Bug fixes: Write reproduction test → Fix code → Verify test passes

# Restrictions
- ❌ DO NOT modify `/prisma/schema.prisma` (requires team review)
- ❌ DO NOT install new dependencies (discuss in package.json review)
- ❌ DO NOT modify `/lib/auth/*` (authentication logic is sensitive)
- ✅ CAN freely modify business code under `/components` and `/app`

This prevents AI from “helping” in the wrong ways, accidentally modifying critical code.

7 Tips to Double Effectiveness

Tip 1: Use SHOULD/MUST to Emphasize Priority

Not all rules are equally important. Use keywords to differentiate priority.

# Rule Priority
**MUST (mandatory)**
- MUST use TypeScript strict mode
- MUST add error handling to all APIs

**SHOULD (recommended)**
- SHOULD keep components under 200 lines
- SHOULD extract repeated logic as custom Hooks

**COULD (optional)**
- COULD add JSDoc comments

This technique comes from RFC specification documents. After using it, Claude clearly enforces “MUST” rules more strictly.

Tip 2: Leverage the /init Command

Although official docs say CLAUDE.md loads automatically, I strongly recommend running /init every time you open a project.

You: /init
Claude: Project config loaded, current tech stack: React 18 + TypeScript...

It’s like “refreshing” AI’s memory. Especially when you just modified CLAUDE.md, /init makes changes take effect immediately.

Tip 3: Example Code Beats Thousand Words

Rather than describing standards, show examples directly.

❌ Pure text description:

- API functions need type definitions, error handling, and loading states

✅ With code example:

# API Call Standards
Reference example:
\`\`\`typescript
// src/services/user.ts
export async function getUser(id: string): Promise<User> {
  try {
    const response = await fetch(`/api/users/${id}`);
    if (!response.ok) throw new Error('Failed to fetch user');
    return await response.json();
  } catch (error) {
    console.error('getUser error:', error);
    throw error;
  }
}
\`\`\`
All API functions follow this pattern: typed return + try-catch + error logging

After seeing examples, Claude generates code very close to your expectations.

Tip 4: Layered Configuration (Monorepo Essential)

If your project is Monorepo architecture, definitely use layered configuration.

monorepo-root/
├── CLAUDE.md                    # Global: general standards, Git workflow
├── apps/
│   ├── web/
│   │   └── .claude/CLAUDE.md   # Web app: React + Next.js
│   └── mobile/
│       └── .claude/CLAUDE.md   # Mobile: React Native
└── packages/
    └── shared/
        └── .claude/CLAUDE.md   # Shared: Pure TS utility library

Root CLAUDE.md (global standards):

# Monorepo Common Standards
- Use pnpm as package manager
- Unified TypeScript config inherits from root tsconfig.json
- Commit messages follow Conventional Commits

# Workflow
- Run `pnpm install` before code changes
- Run `pnpm run lint` to check all packages before commit

apps/web/.claude/CLAUDE.md (frontend-specific):

# Web Application Config
Inherits root standards, additional config below:

- Tech stack: Next.js 14 + React 18
- Styling: Tailwind CSS
- State management: Zustand

Claude reads root config first, then reads sub-config based on your current working directory. This way you don’t repeat common standards in each subproject.

Tip 5: Use ❌ and ✅ for Comparison

Both humans and AI love learning through contrast.

# State Update Standards

❌ Wrong: Direct state mutation
\`\`\`typescript
const [user, setUser] = useState({name: 'John', age: 30});
user.age = 31; // Wrong! Directly mutated object
\`\`\`

✅ Correct: Immutable update
\`\`\`typescript
const [user, setUser] = useState({name: 'John', age: 30});
setUser(prev => ({...prev, age: 31}));
\`\`\`

This contrast makes rules crystal clear, and Claude learns more efficiently.

Tip 6: Document Common Error Patterns

Write down errors your team frequently makes, let AI help guard against them.

# ⚠️ Common Mistakes and Pitfall Guide

## 1. Forgetting to Cleanup Side Effects
❌ Problem code:
\`\`\`typescript
useEffect(() => {
  const timer = setInterval(() => {/* ... */}, 1000);
  // Forgot to cleanup!
}, []);
\`\`\`

✅ Correct approach:
\`\`\`typescript
useEffect(() => {
  const timer = setInterval(() => {/* ... */}, 1000);
  return () => clearInterval(timer); // Cleanup timer
}, []);
\`\`\`

## 2. Missing Dependencies
If ESLint warns about missing dependencies, don't disable the warning—either add dependency or optimize with useCallback/useMemo

With this, Claude proactively avoids these pitfalls when generating code.

Tip 7: Link to Detailed Documentation

CLAUDE.md should be concise, but can link to detailed docs.

# Detailed Standards Documentation
- [API Design Guidelines](./docs/api-guidelines.md) - RESTful API design standards
- [Component Development Guide](./docs/component-guide.md) - Component splitting and reuse principles
- [Testing Standards](./docs/testing.md) - Unit and integration test requirements

This keeps CLAUDE.md concise while providing detailed information when needed. Claude can access more context through these links.

5 Most Common Pitfalls

Pitfall 1: File Too Long, Cramming Everything

Most common beginner mistake. Stuffing README, API docs, business logic explanations all into CLAUDE.md.

Problem: Consumes too many tokens, actually dilutes important information. Solution: Strictly keep under 100 lines, only write what AI truly needs for coding.

Pitfall 2: Never Updating Config

Project changes, but CLAUDE.md stays the same.

Problem: Outdated config causes AI to generate wrong code. Solution: Develop a habit—update CLAUDE.md after major refactors, and review config changes in PRs.

Pitfall 3: Forgetting Version Control

Adding CLAUDE.md to .gitignore or not committing to repository.

Problem: Team members each do their own thing, code style becomes chaotic. Solution: Must include in Git, review together with code.

Pitfall 4: Overly Generic Rules

Writing vague phrases like “keep code concise,” “follow best practices.”

Problem: AI can’t execute, equivalent to not writing anything. Solution: Each rule must be specific, verifiable, actionable.

Pitfall 5: Sensitive Information Leakage

Writing API keys, database passwords into CLAUDE.md.

Problem: Config files get committed to repository, exposing sensitive info. Solution: Only describe configuration approach, don’t write actual values.

❌ Wrong
\`\`\`markdown
# Database Config
DATABASE_URL=postgresql://admin:password123@localhost:5432/mydb
\`\`\`

✅ Correct
\`\`\`markdown
# Environment Variables
- DATABASE_URL: Read from .env.local, format reference .env.example
- API_KEY: Get from environment variables, contact @Zhang San for dev test key
\`\`\`

3 Real Project Examples

Example 1: React Frontend Project

This is a simplified version of an e-commerce frontend project I’m currently maintaining:

# E-commerce Frontend Project

## Tech Stack
- Next.js 14.0 (App Router)
- React 18.2
- TypeScript 5.2
- Tailwind CSS 3.4
- Zustand (state management)
- TanStack Query (server state)

## Project Structure
src/
├── app/          # Page routes
├── components/   # Components
│   ├── ui/      # Base components
│   └── features/ # Business components
├── lib/         # Utility functions
└── services/    # API calls

## Coding Standards
- Components: Function components + Hooks
- State: Local with useState, global with Zustand, server with TanStack Query
- Styling: Tailwind utilities, extract complex layouts as components
- Error handling: API calls MUST use try-catch

## Commands
npm run dev      # Dev server
npm run build    # Production build
npm run lint     # Code check

## Restrictions
- DO NOT modify /lib/auth/* (authentication logic)
- DO NOT install new packages (needs team discussion)

Result: After using this config, components Claude generates match my hand-written ones, saving massive adjustment time.

Example 2: Node.js Backend Project

This is configuration for an Express API project:

# Order Management System API

## Tech Stack
- Node.js 20 LTS
- Express 4.18
- Prisma ORM
- PostgreSQL 15
- Zod (data validation)

## Project Structure
src/
├── routes/       # Route definitions
├── controllers/  # Business logic
├── services/     # Database operations
├── middleware/   # Middleware
└── utils/        # Utility functions

## Coding Standards
- All APIs MUST include: request validation (Zod) + error handling + logging
- Database operations unified in services layer
- Controllers only handle request/response, no business logic
- Use async/await, avoid callbacks

## API Example
\`\`\`typescript
// controllers/order.controller.ts
export async function createOrder(req: Request, res: Response) {
  try {
    const data = orderSchema.parse(req.body); // Zod validation
    const order = await orderService.create(data);
    logger.info('Order created', { orderId: order.id });
    res.json({ success: true, data: order });
  } catch (error) {
    logger.error('Create order failed', error);
    res.status(500).json({ success: false, error: 'Internal error' });
  }
}
\`\`\`

## Commands
npm run dev       # Dev mode (nodemon)
npm run build     # TypeScript compile
npm test          # Jest tests
npx prisma studio # Database GUI

Result: Claude now generates API endpoints with built-in Zod validation and error handling—quality significantly improved.

Example 3: Monorepo Architecture

This is a Monorepo project containing both frontend and backend:

Root CLAUDE.md:

# Full-stack Application Monorepo

## Architecture
- Using pnpm workspaces
- apps/: Applications
- packages/: Shared packages

## Common Standards
- TypeScript strict mode
- ESLint + Prettier unified formatting
- Commits follow Conventional Commits

## Commands
pnpm install           # Install all dependencies
pnpm run dev           # Start both frontend and backend
pnpm run lint          # Check all packages
pnpm --filter web dev  # Start only web app

apps/web/.claude/CLAUDE.md:

# Web Application Config
Inherits root standards

- Next.js 14 + React
- Port: 3000
- Detailed standards see root CLAUDE.md

apps/api/.claude/CLAUDE.md:

# API Service Config
Inherits root standards

- Express + Prisma
- Port: 4000
- Detailed standards see root CLAUDE.md

Result: Claude switches context automatically based on current working directory, generating React code in frontend directory and Express code in backend directory.

Conclusion: Start Optimizing Your CLAUDE.md Today

After reading these 7 tips, you should have a clear understanding of how to write effective CLAUDE.md. Remember the three most important points:

1. Keep it concise - Under 100 lines, only essential information
2. Be specific enough - Each rule is actionable and verifiable
3. Continuous updates - Project changes, config should change too

From my actual experience, a good CLAUDE.md can boost AI work efficiency by at least 30%. You don’t need to write everything at once—start with basic tech stack declaration, then each time AI makes a mistake, add a rule to CLAUDE.md.

Open your project now and create or optimize your CLAUDE.md. If you haven’t started using Claude Code, this config file will be your first step. If you’re already using it but AI performance isn’t ideal, try these tips I shared today.

One final reminder: CLAUDE.md isn’t a one-time task—it should grow with your project. Every major refactor, tech stack upgrade, or standard change, don’t forget to update this file. Helping AI truly understand your project starts with writing good CLAUDE.md.

Published on: Nov 22, 2025 · Modified on: Dec 4, 2025

Easton

AI & Intelligence