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claude-md

Create or update CLAUDE.md files following best practices for optimal AI agent onboarding

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SKILL.md
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User Input

$ARGUMENTS

You MUST consider the user input before proceeding (if not empty). User may specify:

  • create - Create new CLAUDE.md from scratch
  • update - Improve existing CLAUDE.md
  • audit - Analyze and report on current CLAUDE.md quality
  • A specific path to create/update (e.g., src/api/CLAUDE.md for directory-specific instructions)

Core Principles

LLMs are stateless: CLAUDE.md is the only file automatically included in every conversation. It serves as the primary onboarding document for AI agents into your codebase.

The Golden Rules

  1. Less is More: Frontier LLMs can follow ~150-200 instructions. Claude Code's system prompt already uses ~50. Keep your CLAUDE.md focused and concise.

  2. Universal Applicability: Only include information relevant to EVERY session. Task-specific instructions belong in separate files.

  3. Don't Use Claude as a Linter: Style guidelines bloat context and degrade instruction-following. Use deterministic tools (prettier, eslint, etc.) instead.

  4. Never Auto-Generate: CLAUDE.md is the highest leverage point of the AI harness. Craft it manually with careful consideration.

Execution Flow

1. Project Analysis

First, analyze the current project state:

  1. Check for existing CLAUDE.md files:

    • Root level: ./CLAUDE.md or .claude/CLAUDE.md
    • Directory-specific: **/CLAUDE.md
    • Global user config: ~/.claude/CLAUDE.md
  2. Identify the project structure:

    • Technology stack (languages, frameworks)
    • Project type (monorepo, single app, library)
    • Development tools (package manager, build system, test runner)
  3. Review existing documentation:

    • README.md
    • CONTRIBUTING.md
    • package.json, pyproject.toml, Cargo.toml, etc.

2. Content Strategy (WHAT, WHY, HOW)

Structure CLAUDE.md around three dimensions:

WHAT - Technology & Structure

  • Technology stack overview
  • Project organization (especially important for monorepos)
  • Key directories and their purposes

WHY - Purpose & Context

  • What the project does
  • Why certain architectural decisions were made
  • What each major component is responsible for

HOW - Workflow & Conventions

  • Development workflow (bun vs node, pip vs uv, etc.)
  • Testing procedures and commands
  • Verification and build methods
  • Critical "gotchas" or non-obvious requirements

3. Progressive Disclosure Strategy

For larger projects, recommend creating an agent_docs/ folder:

agent_docs/
  |- building_the_project.md
  |- running_tests.md
  |- code_conventions.md
  |- architecture_decisions.md

In CLAUDE.md, reference these files with instructions like:

For detailed build instructions, refer to `agent_docs/building_the_project.md`

Important: Use file:line references instead of code snippets to avoid outdated context.

4. Quality Constraints

When creating or updating CLAUDE.md:

  1. Target Length: Keep it under a few hundred lines; shorter is better
  2. No Style Rules: Remove any linting/formatting instructions
  3. No Task-Specific Instructions: Move to separate files
  4. No Code Snippets: Use file references instead
  5. No Redundant Information: Don't repeat what's in package.json or README

5. Essential Sections

A well-structured CLAUDE.md should include:

# Project Name

Brief one-line description.

## Tech Stack
- Primary language and version
- Key frameworks/libraries
- Database/storage (if any)

## Project Structure
[Only for monorepos or complex structures]
- `apps/` - Application entry points
- `packages/` - Shared libraries

## Development Commands
- Install: `command`
- Test: `command`
- Build: `command`

## Critical Conventions
[Only non-obvious, high-impact conventions]
- Convention 1 with brief explanation
- Convention 2 with brief explanation

## Known Issues / Gotchas
[Things that consistently trip up developers]
- Issue 1
- Issue 2

6. Anti-Patterns to Avoid

DO NOT include:

  • Code style guidelines (use linters)
  • Documentation on how to use Claude
  • Long explanations of obvious patterns
  • Copy-pasted code examples
  • Generic best practices ("write clean code")
  • Instructions for specific tasks
  • Auto-generated content
  • Extensive TODO lists

7. Validation Checklist

Before finalizing, verify:

  • Kept under a few hundred lines; shorter is better
  • Every line applies to ALL sessions
  • No style/formatting rules
  • No code snippets (use file references)
  • Commands are verified to work
  • Progressive disclosure used for complex projects
  • Critical gotchas are documented
  • No redundancy with README.md

Output Format

For create or default:

  1. Analyze the project
  2. Draft a CLAUDE.md following the structure above
  3. Present the draft for review
  4. Write to the appropriate location after approval

For update:

  1. Read existing CLAUDE.md
  2. Audit against best practices
  3. Identify:
    • Content to remove (style rules, code snippets, task-specific)
    • Content to condense
    • Missing essential information
  4. Present changes for review
  5. Apply changes after approval

For audit:

  1. Read existing CLAUDE.md
  2. Generate a report with:
    • Current line count vs target
    • Percentage of universally-applicable content
    • List of anti-patterns found
    • Recommendations for improvement
  3. Do NOT modify the file, only report

AGENTS.md Handling

If the user requests AGENTS.md creation/update:

AGENTS.md is used for defining specialized agent behaviors. Unlike CLAUDE.md (which is for project context), AGENTS.md defines:

  • Custom agent roles and capabilities
  • Agent-specific instructions and constraints
  • Workflow definitions for multi-agent scenarios

Apply similar principles:

  • Keep focused and concise
  • Use progressive disclosure
  • Reference external docs instead of embedding content

Notes

  • Always verify commands work before including them
  • When in doubt, leave it out - less is more
  • The system reminder tells Claude that CLAUDE.md "may or may not be relevant" - the more noise, the more it gets ignored
  • Monorepos benefit most from clear WHAT/WHY/HOW structure
  • Directory-specific CLAUDE.md files should be even more focused
Repository
luongnv89/claude-howto
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