name: phase-4-api description: | Skill for designing and implementing backend APIs. Includes Zero Script QA methodology for API validation.

Use proactively when user needs to design or implement backend APIs.

Triggers: API design, REST API, backend, endpoint, API 설계, 백엔드, 엔드포인트, API設計, バックエンド, API设计, 后端, diseño de API, backend, conception API, backend, API-Design, Backend, progettazione API, backend

Do NOT use for: frontend-only projects, Starter level

──── NEW FIELDS (v1.5.1) ────

user-invocable: true argument-hint: ""

allowed-tools:

• read_file
• write_file
• replace
• glob
• grep_search
• run_shell_command

imports:

• templates/design.template.md

agents: {}

context: session memory: project pdca-phase: do

Phase 4: API Design & Implementation

Build robust backend APIs

Deliverables

1. API Specification

OpenAPI/Swagger format:

openapi: 3.0.0
info:
  title: User API
  version: 1.0.0

paths:
  /api/users:
    get:
      summary: List users
      responses:
        '200':
          description: User list
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/User'

    post:
      summary: Create user
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/CreateUser'

2. Endpoint Implementation

// app/api/users/route.ts
import { NextRequest, NextResponse } from 'next/server';

export async function GET(request: NextRequest) {
  const users = await db.user.findMany();
  return NextResponse.json(users);
}

export async function POST(request: NextRequest) {
  const body = await request.json();
  const user = await db.user.create({ data: body });
  return NextResponse.json(user, { status: 201 });
}

3. Error Handling

// Standard error response
{
  "error": {
    "code": "VALIDATION_ERROR",
    "message": "Invalid email format",
    "details": [
      { "field": "email", "message": "Must be a valid email" }
    ]
  }
}

API Patterns

• RESTful resource naming
• Consistent response format
• Proper HTTP status codes
• Input validation
• Rate limiting

Output

Save to: docs/02-design/api-spec.yaml

Next Phase

After completion: /phase-5-design-system or /phase-6-ui-integration