Extract as Rule

Rules apply to specific file paths or patterns. Extract when a requirement is NOT universal, but specific to certain directories, file types, or layers.

1. Identify the Scope

Rules apply to:

• •Directories: services/**/*.ts, frontend/components/**/*.tsx
• •File types: *.test.ts, *.config.js, *.md
• •Layers: "API handlers", "utility functions", "tests"
• •Combinations: services/**/*.ts but exclude **/*.test.ts

Glob patterns:

• •**/*.ts — all TypeScript files recursively
• •services/** — everything under services/
• •!services/**/*.test.ts — exclude test files
• •{src,lib}/**/*.js — either src or lib directory

2. Extract the Requirement

What must be true for files matching this scope?

• •"Must include error handling"
• •"Must have JSDoc comments"
• •"Must not exceed 200 lines"
• •"Must use async/await, not callbacks"

3. Name the Rule File

Location: ~/.claude/rules/<topic>.md

Good names:

• •typescript-services.md — rules for service files
• •python-conventions.md — Python-specific standards
• •test-requirements.md — testing standards
• •security-guidelines.md — security requirements

4. Create the Rule File

Template:

---
paths:
  - "services/**/*.ts"
  - "!services/**/*.test.ts"
---

# Backend Service Standards

These rules apply to all service TypeScript files.

## Error Handling
[requirement and why]

## Logging
[requirement and why]

## Type Safety
[requirement and why]

## Documentation
[requirement and why]

5. Multiple Rules in One File

You can group related rules:

---
paths:
  - "services/**/*.ts"
  - "lib/**/*.ts"
---

# TypeScript Standards (Services & Lib)

## Error Handling
...

## Testing
...

Or create separate files by concern:

~/.claude/rules/
├── typescript-services.md
├── python-testing.md
├── documentation.md
└── security.md

6. Reference in Projects

In your project's .claude/CLAUDE.md:

## Project Rules

See @~/.claude/rules/typescript-services.md for backend standards.

Example Output

✓ Created rule: ~/.claude/rules/backend-standards.md
Applies to: services/**/*.ts

I'll apply this rule when reviewing code in those paths.
In projects, reference it with: @~/.claude/rules/backend-standards.md

Common Rule Categories

• •Language conventions (TypeScript, Python, JavaScript patterns)
• •Layer-specific requirements (API handlers, utilities, tests)
• •Quality standards (line length, complexity, documentation)
• •Security requirements (input validation, error handling)
• •Testing standards (coverage requirements, test patterns)
• •Documentation (what each layer should document)