CLAUDE.md Initialization Guidance

CLAUDE.md Best Practices

When creating or initialising a CLAUDE.md file, follow these guidelines to produce an effective, high-quality project context file.

Core Principles

CLAUDE.md is the highest leverage point for Claude Code. It affects every workflow phase and output artifact. Treat it as carefully crafted documentation, not auto-generated content.

The Three Essential Sections

Structure every CLAUDE.md around three core areas:

WHAT - Describe the codebase:

• Tech stack and major dependencies
• Project structure and directory layout
• Key files and their purposes
• Important for monorepos: provide a clear map

WHY - Explain the purpose:

• What the project does
• Why components exist
• Business context when relevant

HOW - Detail workflows (only essential):

• Build and run commands
• Test execution methods
• Deployment procedures
• Verification steps

Critical Constraints

Keep It Concise

Target fewer than 300 lines. Aim for under 60 lines when possible.

Every line in CLAUDE.md competes for attention. Irrelevant context degrades performance uniformly across all instructions. Remove anything not universally applicable to every task.

Respect Instruction Limits

Include only critical project-specific rules and essential workflow commands.

Use Progressive Disclosure

Store detailed, task-specific guidance in separate files. Reference them from CLAUDE.md rather than embedding everything in CLAUDE.md.

Instead of:

## API Development
[500 lines of API documentation]

Use:

## API Development
See `docs/api-guide.md` for API development guidelines.

Read the projects documentation and its structure to determine which files to reference.

Avoid Style Guidelines

Do not use CLAUDE.md for code style enforcement. Deterministic tools handle this better

Style instructions in CLAUDE.md waste instruction budget and produce inconsistent results. Configure tooling instead.

Use File:Line Pointers

Reference code locations instead of embedding snippets:

Instead of:

The authentication middleware looks like:
\`\`\`typescript
export function authMiddleware(req, res, next) {
  // 50 lines of code
}
\`\`\`

Use:

Authentication middleware: `src/middleware/auth.ts:15`

Benefits:

• Stays current as code changes
• Reduces CLAUDE.md size
• Claude reads the actual file when needed

Writing Guidelines

Be Direct and Specific

State facts and commands clearly:

Good:

Run tests: `npm test`
Build: `npm run build`
Database: PostgreSQL 14

Avoid:

You might want to run tests using npm test.
The build process can be initiated with npm run build.
We use PostgreSQL for our database needs.

Prioritize Ruthlessly

Ask yourself for each line:

• Does this apply to every task?
• Is this information Claude cannot infer?
• Would removing this cause problems?

What to Include

Always Include

• Primary language and version
• Framework and major dependencies
• Essential build/run/test commands
• Project structure overview (brief)
• Critical conventions that differ from defaults

Consider Including

• Database and infrastructure details
• Environment setup requirements
• Key architectural decisions
• Important file locations

Never Include

• Obvious information Claude can infer
• Code snippets (use file:line references)
• Style guides (use linters)
• Comprehensive documentation (link to it)
• Information for specific tasks only

Anti-Patterns to Avoid

The Kitchen Sink

Including everything "just in case" dilutes important instructions. Be selective.

The Style Guide

Embedding coding standards. Use tooling instead.

The Tutorial

Explaining how things work in detail. Link to documentation.

The Changelog

Including historical context or version notes. Keep it current-state only.

The Copy-Paste

Embedding code blocks. Use file:line references.

Final Checklist

Before finalizing CLAUDE.md:

• Under 300 lines (ideally under 60)
• Has WHAT, WHY, HOW sections
• No code snippets (file:line references instead)
• No style guidelines (tooling handles this)
• Task-specific details in separate files
• Every line applies to every task
• Direct, specific language
• Manually crafted, not auto-generated