---

name: api-development description: "Develop and test API routes in the Next.js App Router. Use this when the user asks to create, modify, test, or debug API endpoints, handle API responses, validate request parameters, or work with the /api directory." allowed-tools: Read, Edit, Write, Grep, Glob, Bash

API Development Skill

This Skill helps develop, test, and debug API routes in the IsLeapYear Next.js application.

When to Use

• Creating new API endpoints
• Modifying existing API routes
• Testing API responses
• Debugging API errors
• Validating request parameters
• Working with API response helpers

Key Patterns

API Route Structure

All API routes follow Next.js 15 App Router patterns with async params:

Copyexport const GET = async (
  request: NextRequest,
  { params }: { params: Promise<{ year: string }> }
) => {
  const { year: yearParam } = await params;
  const year = Number.parseInt(yearParam, 10);

  if (Number.isNaN(year)) {
    return errorResponse("Invalid year parameter");
  }

  return successResponse({ result: someData });
};

Response Helpers

Located in src/utils/response.ts:

• successResponse<T>(data: T) - Returns 200 with standardized format
• errorResponse(message: string, status?: number) - Returns error response

Response format:

Copy{
  "status": 200,
  "data": { ... },
  "meta": { "timestamp": "2025-01-15T..." }
}

API Directory Structure

Copysrc/app/api/
├── check/              # Leap year check endpoints
│   ├── [year]/        # Single year: /api/check/2024
│   ├── batch/         # Batch checks
│   └── route.ts       # Current year
├── calendar/          # Multi-calendar support
│   └── [type]/check/[year]/
└── stats/             # Statistics
    ├── range/
    └── distribution/

Testing Commands

Copy# Test current year endpoint
curl http://localhost:3000/api/check

# Test specific year
curl http://localhost:3000/api/check/2024

# Test batch endpoint
curl -X POST http://localhost:3000/api/check/batch \
  -H "Content-Type: application/json" \
  -d '{"years": [2024, 2025, 2026]}'

# Test calendar type
curl http://localhost:3000/api/calendar/gregorian/check/2024

Common Tasks

1. Creating a New Endpoint

1. Determine the route path (e.g., /api/check/validate/[year])
2. Create the directory structure
3. Create route.ts with GET/POST handlers
4. Use response helpers from utils/response.ts
5. Validate all inputs
6. Test with curl commands

2. Validating Parameters

Always validate:

• Year ranges (1582-9999 for Gregorian)
• Number parsing (use Number.parseInt and check Number.isNaN)
• Required fields for POST requests
• Calendar types (gregorian, julian, hebrew, chinese)

3. Error Handling

Return appropriate errors:

• 400 for invalid parameters
• 404 for not found
• 500 for server errors

Use errorResponse() helper for consistency.

Important Notes

• Always use async functions for route handlers
• Always await params in dynamic routes (Next.js 15 requirement)
• Use TypeScript for all routes
• Import response helpers: import { successResponse, errorResponse } from "@/utils/response"
• Test locally before deployment
• Follow the satirical tone for error messages when appropriate