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