api-endpoint-builder

API Endpoint Builder

Build complete, production-ready REST API endpoints 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

// 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:

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