api-endpoint-builder

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• README.md
• SKILL.md

SKILL.md (first lines)

# API Endpoint Builder

Build complete, reviewable REST API endpoint scaffolds with proper validation, error handling, authentication, and documentation.

## When to Use This Skill

- User asks to "create an API endpoint" or "build a REST API"
- Building new backend features
- Adding endpoints to existing APIs
- User mentions "API", "endpoint", "route", or "REST"
- Creating CRUD operations

## What You'll Build

For each endpoint, you create:
- Route handler with proper HTTP method
- Input validation (request body, params, query)
- Authentication/authorization checks
- Business logic
- Error handling
- Response formatting
- API documentation
- Tests (if requested)

## Endpoint Structure

### 1. Route Definition

```javascript
// Express example
router.post('/api/users', authenticate, validateUser, createUser);

// Fastify example
fastify.post('/api/users', {
  preHandler: [authenticate],
  schema: userSchema
}, createUser);
```

### 2. Input Validation

Always validate before processing:

```javascript
const validateUser = (req, res, next) => {
  const { email, name, password } = req.body ?? {};
  
  if (typeof email !== 'string' || !email.includes('@')) {
    return res.status(400).json({ error: 'Valid email required' });
  }
  
  if (typeof name !== 'string' || name.trim().length < 2) {
    return res.status(400).json({ error: 'Name must be at least 2 characters' });
  }
  
  if (typeof password !== 'string' || password.length < 8) {
    return res.status(400).json({ error: 'Password must be at least 8 characters' });
  }
  
  next();
};
```

### 3. Handler Implementation

```javascript
const createUser = async (req, res) => {
  try {
    const { email, name, password } = req.body ?? {};
    
    // Check if user exists
    const existing = await db.users.findOne({ email });
    if (existing) {
      return res.status(409).json({ error: 'User already exists' });
    }
    
    // Hash password
    const hashedPassword = await bcrypt.hash(password, 10);
    
    // Create user
    const user = await db.users.create({
      email,
      name,
      password: hashedPassword,
      createdAt: new Date()
    });
    
    // Don't return password
    const userWithoutPassword = { id: user.id, email: user.email, name: user.name };
    
    res.status(201).json({
      success: true,
      data: userWithoutPassword
    });
    
  } catch (error) {
    console.error('Create user error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
};
```

## Best Practices

### HTTP Status Codes
- `200` - Success (GET, PUT, PATCH)
- `201` - Created (POST)
- `204` - No Content (DELETE)
- `400` - Bad Request (validation failed)
- `401` - Unauthorized (not authenticated)
- `403` - Forbidden (not authorized)
- `404` - Not Found
- `409` - Conflict (duplicate)
- `500` - Internal Server Error

### Response Format

Consistent structure:

From sickn33/agentic-awesome-skills, MIT.

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