Master Claude Code in a Week (Part 6): Skills

This is the sixth part of the "Master Claude Code in a Week" series. In this article, we'll explore Skills — reusable capabilities that are automatically triggered.

What are Skills?

Skills are reusable capabilities — collections of instructions, scripts, and templates that are automatically triggered when Claude detects a matching context. Unlike Slash Commands (manual trigger), Skills are invoked based on conversation content.

┌────────────────────────────────────────────────────────────────┐
│                          SKILLS                                 │
├────────────────────────────────────────────────────────────────┤
│                                                                 │
│   User: "Review this code for security issues"                 │
│                    │                                           │
│                    ▼                                           │
│   ┌────────────────────────────────────────┐                  │
│   │ Claude detects: "code review" + "security"                │
│   └────────────────────────────────────────┘                  │
│                    │                                           │
│                    ▼                                           │
│   ┌────────────────────────────────────────┐                  │
│   │ Auto-invokes: security-review skill     │                  │
│   │                                         │                  │
│   │ ~/.claude/skills/security-review/       │                  │
│   │ ├── SKILL.md (instructions)             │                  │
│   │ ├── scripts/scan.sh                     │                  │
│   │ └── templates/report.md                 │                  │
│   └────────────────────────────────────────┘                  │
│                    │                                           │
│                    ▼                                           │
│   Comprehensive security review executed                       │
│                                                                 │
└────────────────────────────────────────────────────────────────┘

Skills vs Slash Commands

Skill Structure

skill-name/
├── SKILL.md           # Main instructions (required)
├── scripts/           # Helper scripts (optional)
│   ├── analyze.sh
│   └── report.py
├── templates/         # Output templates (optional)
│   ├── summary.md
│   └── report.json
└── examples/          # Example files (optional)
    └── sample-output.md

SKILL.md Structure

---
name: skill-name
description: Brief description for Claude to match
triggers:
  - "trigger phrase 1"
  - "trigger phrase 2"
---

# Skill Name

## Purpose
What this skill does.

## When to Use
Conditions that should trigger this skill.

## Instructions
Step-by-step instructions for Claude.

## Scripts Available
- `scripts/analyze.sh`: Description
- `scripts/report.py`: Description

## Templates
- `templates/summary.md`: For final summary
- `templates/report.json`: For structured output

## Output Format
Expected output structure.

Installing Skills

Storage Locations

Personal (global):

~/.claude/skills/

Project-specific:

.claude/skills/

From claude-howto

# Copy all skills
cp -r claude-howto/03-skills/* ~/.claude/skills/

# Or copy specific skill
cp -r claude-howto/03-skills/code-review ~/.claude/skills/

Example Skills

1. Code Review Skill

Location: ~/.claude/skills/code-review/

SKILL.md:

---
name: code-review
description: Comprehensive code review with best practices
triggers:
  - "review this code"
  - "code review"
  - "check this code"
  - "review PR"
---

# Code Review Skill

## Purpose
Perform comprehensive code review covering quality, security, 
performance, and maintainability.

## When to Use
- When user asks for code review
- When reviewing pull requests
- When checking code quality

## Instructions

### 1. Initial Analysis
- Identify the programming language
- Understand the code's purpose
- Note the architecture/patterns used

### 2. Quality Check
Run through checklist:
- [ ] Clean code principles followed
- [ ] Proper naming conventions
- [ ] Single responsibility principle
- [ ] DRY (Don't Repeat Yourself)
- [ ] Error handling present

### 3. Security Review
Check for:
- SQL injection vulnerabilities
- XSS vulnerabilities
- Authentication/Authorization issues
- Sensitive data exposure
- Input validation

### 4. Performance Analysis
Look for:
- N+1 query problems
- Unnecessary loops
- Memory leaks
- Caching opportunities
- Algorithm efficiency

### 5. Generate Report
Use template: `templates/review-report.md`

## Output Format

## Code Review Summary

### Overall Score: X/10

### Critical Issues (Must Fix)
- [Issue with file:line reference]

### Major Issues (Should Fix)
- [Issue with file:line reference]

### Minor Issues (Nice to Have)
- [Issue with file:line reference]

### Positive Aspects
- [Good practice noted]

### Recommendations
1. [Actionable suggestion]
2. [Actionable suggestion]

2. Documentation Generator Skill

Location: ~/.claude/skills/doc-generator/

SKILL.md:

---
name: doc-generator
description: Generate technical documentation automatically
triggers:
  - "generate docs"
  - "document this"
  - "create documentation"
  - "write docs"
---

# Documentation Generator Skill

## Purpose
Automatically generate comprehensive technical documentation.

## When to Use
- When user asks for documentation
- When documenting APIs
- When creating README files

## Instructions

### 1. Analyze Code
- Identify public interfaces
- Extract function signatures
- Find existing comments/docstrings

### 2. Determine Doc Type
- API Documentation
- README
- Architecture Doc
- User Guide
- Code Comments

### 3. Generate Documentation

#### For API Documentation:
- Endpoint path and method
- Parameters (path, query, body)
- Request/Response examples
- Error codes

#### For README:
- Project description
- Installation steps
- Usage examples
- Configuration options
- Contributing guidelines

### 4. Format Output
Use appropriate template from `templates/`

3. Brand Voice Skill

Location: ~/.claude/skills/brand-voice/

SKILL.md:

---
name: brand-voice
description: Ensure content matches brand voice guidelines
triggers:
  - "write in brand voice"
  - "brand guidelines"
  - "marketing copy"
  - "content review for brand"
---

# Brand Voice Skill

## Purpose
Review and generate content that matches brand voice guidelines.

## When to Use
- Writing marketing copy
- Creating user-facing messages
- Reviewing content for brand consistency

## Instructions

### 1. Load Brand Guidelines
Check for brand guidelines in:
1. `CLAUDE.md` (Brand Voice section)
2. `.claude/brand-voice.md`
3. `docs/brand-guidelines.md`

### 2. Analyze Content
- Tone: Formal vs Casual
- Voice: Active vs Passive
- Vocabulary: Technical level
- Personality: Brand attributes

### 3. Review/Generate

#### For Review:
- Highlight inconsistencies
- Suggest alternatives
- Score brand alignment

#### For Generation:
- Apply brand voice rules
- Use approved vocabulary
- Match tone guidelines

Create Your Own Skill

Step 1: Create folder structure

mkdir -p ~/.claude/skills/my-skill/{scripts,templates,examples}
touch ~/.claude/skills/my-skill/SKILL.md

Step 2: Define SKILL.md

---
name: my-skill
description: What this skill does
triggers:
  - "trigger phrase"
---

# My Skill

## Purpose
What this skill accomplishes.

## When to Use
Conditions for triggering.

## Instructions
Step-by-step guide.

## Output Format
Expected output structure.

Step 3: Add scripts (optional)

# scripts/helper.sh
#!/bin/bash
# Helper script
echo "Running helper..."

Step 4: Add templates (optional)

# templates/output.md
# {{title}}

## Summary
{{summary}}

## Details
{{details}}

Step 5: Test

Ask Claude something that should trigger your skill:

User: "Please generate docs"  # Should trigger doc-generator
User: "Review this code"      # Should trigger code-review

Skills from Community

Claude-howto provides a skills collection at luongnv89/skills:

Available Skills

Install from collection

# Clone skills repository
git clone https://github.com/luongnv89/skills.git

# Install specific skill
cp -r skills/code-review ~/.claude/skills/

# Install all skills
cp -r skills/* ~/.claude/skills/

Best Practices

1. Clear Triggers

# ❌ Bad - Too generic
triggers:
  - "help"
  - "do something"

# ✅ Good - Specific
triggers:
  - "review code for security"
  - "security audit"
  - "check vulnerabilities"

2. Detailed Instructions

# ❌ Bad - Vague
## Instructions
Review the code.

# ✅ Good - Detailed
## Instructions
### 1. Initial Analysis
- Identify programming language
- Note architecture patterns
- List dependencies

### 2. Security Check
For each category:
- [ ] SQL Injection: Check for parameterized queries
- [ ] XSS: Check for output encoding
- [ ] Auth: Check for proper authentication

3. Useful Scripts

Keep scripts focused and reusable:

#!/bin/bash
# ✅ Good - Single purpose, reusable
# scripts/count-lines.sh

FILE=$1
if [ -z "$FILE" ]; then
    echo "Usage: count-lines.sh <file>"
    exit 1
fi

wc -l < "$FILE"

Debugging Skills

Skill not triggering

1. Check triggers: Ensure trigger phrases match user input
2. Check location: Skill must be in ~/.claude/skills/ or .claude/skills/
3. Check SKILL.md: Has proper YAML frontmatter format

Script not running

1. Check permissions: chmod +x scripts/*.sh
2. Check shebang: #!/bin/bash at top of file
3. Check path: Reference correct relative path

Test skill manually

User: "I want to trigger my code-review skill. 
       Please review this code for security issues."

Summary

Skills are powerful automation tools:

• ✅ Auto-invoked based on context
• ✅ Include scripts and templates
• ✅ Reusable across projects
• ✅ Shareable with team

Next Up

In the next part, we'll explore Hooks — event-driven automation for Claude Code.

References

• Skills - claude-howto
• Skills Collection

This series is translated and expanded from claude-howto — MIT License.