Write Rules

Rule Creator

Create modular rule files for conventions and shared guidelines.

Core Principles

1. Rules = Conventions - Shared guidelines, lower priority than <law>
2. < 50 lines - Auto-injected = token expensive
3. Use paths: - Scope rules to relevant files only
4. No procedures - How-to belongs in skills
5. NOT for laws - Constitution uses <law> in CLAUDE.md

Rule Structure

.claude/rules/
├── code-style.md         # Style conventions (global)
├── api/
│   └── conventions.md    # paths: src/api/**
└── testing/
    └── guidelines.md     # paths: **/*.test.ts

File Format

Global Rule (no paths:)

---
# No paths field = applies to ALL contexts
---

# Rule Title

- Constraint 1
- Constraint 2

Path-Scoped Rule

---
paths: src/api/**/*.ts
---

# API Rules

- All endpoints MUST validate input
- MUST use standard error format

Glob Patterns

Example: Code Style Convention

# .claude/rules/code-style.md
---
# Global - no paths
---

# Code Style

- Prefer const over let
- Use descriptive variable names
- Keep functions under 50 lines

Example: Path-Scoped Convention

# .claude/rules/api/conventions.md
---
paths: src/api/**/*.ts
---

# API Conventions

- Use async/await, not callbacks
- Return consistent response shapes
- Log errors with context

Validation Checklist

Before creating a rule:

• Is this a convention/guideline, NOT a law? (laws use <law> in CLAUDE.md)
• < 50 lines?
• Does it need paths: scoping?
• Not duplicating existing rules?
• Written in imperative form?

References

• paths-patterns.md - Advanced glob patterns
• examples.md - Rule examples by domain