claude-md-authoring
Best practices for writing effective CLAUDE.md files. Use when creating, updating, or auditing CLAUDE.md files for projects or directories.
What this skill does
# Writing Effective CLAUDE.md Files ## Philosophy CLAUDE.md is a curated set of **guardrails and pointers**, not a comprehensive manual. Every line is scarce real estate. Focus on constraints and gotchas — things Claude would get wrong without guidance. ## What to Include Prioritize in order: 1. **Critical constraints and gotchas** — non-obvious rules, what breaks if ignored 2. **Key commands** — build, test, lint (the 80% cases) 3. **Architecture overview** — how major components relate, 2-3 sentences max 4. **Conventions that differ from defaults** — only what's surprising ## What to Exclude - Anything Claude can infer from reading code - Standard language/framework conventions - Detailed API documentation (link to docs instead) - Long explanations or tutorials - File-by-file codebase descriptions - Information that changes frequently ## Writing Rules - Short declarative bullets > paragraphs - Never write "Never X" without the preferred alternative - When referencing other docs, pitch *when/why* to read them (e.g., "For FooError, see docs/foo.md") - If guidance exceeds ~5 lines, it belongs in a skill or rule instead ## Root vs Subdirectory **Root** (~100-200 lines): Project-wide constraints, build/test commands, architecture. Loaded every session. **Subdirectory** (<50 lines): Only create when: - Directory has >5 files or >3 subdirectories - Local conventions differ from project standards - Non-obvious constraints specific to this directory Don't repeat parent CLAUDE.md content. Don't explain what's obvious from the directory name. ## When to Use Something Else - **>5 lines of domain knowledge** → Skill (loaded on-demand, not every session) - **File-type-specific constraints** → Rule with `paths` frontmatter - **Deterministic enforcement** → Hook (can't be ignored) ## Auditing Existing CLAUDE.md For each line, ask: "Would Claude's behavior change if I removed this?" If no, cut it. Signs of bloat: - >300 lines - Claude ignores rules despite them being there (context dilution) - Generic best practices Claude already knows - Duplicated information from parent CLAUDE.md files When adding content, always propose **pruning alongside additions**. The file should get tighter over time, not longer.
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