memstack-development-api-designer

🔌 API Designer — Designing routes, validation, and handler patterns...

Produces production-ready Next.js App Router API routes with auth guards, Zod validation, typed responses, and consistent error handling.

Activation

When this skill activates, output:

🔌 API Designer — Designing API routes and handlers...

Then execute the protocol below.

Context	Status
User says "design API" or "create API route" or "add endpoint"	ACTIVE
User says "REST API" or "route handler"	ACTIVE
Building a new feature that needs API routes	ACTIVE
Designing webhook endpoints	ACTIVE
Discussing API concepts or REST theory	DORMANT
Working on frontend components (not API layer)	DORMANT

Anti-patterns

Trap	Reality Check
"Auth is handled by middleware"	Middleware can be bypassed. Every route handler must verify auth independently.
"I'll validate input later"	Unvalidated input is the root of injection, type errors, and 500s. Zod first, logic second.
"Return 200 for everything"	Status codes are the API contract. 401 vs 403 vs 404 vs 422 mean different things to clients.
"Error details help debugging"	Stack traces and internal errors help attackers. Return safe messages, log details server-side.
"Rate limiting is a nice-to-have"	Public endpoints without rate limits get abused within hours of deployment.
"TypeScript types are documentation enough"	Types exist at build time. Zod schemas validate at runtime. You need both.

Protocol

Step 1: Design Route Structure

Map features to Next.js App Router file paths:

app/
  api/
    auth/
      login/route.ts          POST   - authenticate user
      logout/route.ts         POST   - clear session
      callback/route.ts       GET    - OAuth callback
    organizations/
      route.ts                GET    - list user's orgs
                              POST   - create org
      [orgId]/
        route.ts              GET    - get org details
                              PATCH  - update org
                              DELETE - delete org
        members/
          route.ts            GET    - list members
                              POST   - invite member
          [memberId]/
            route.ts          PATCH  - update role
                              DELETE - remove member
        projects/
          route.ts            GET    - list projects
                              POST   - create project
    webhooks/
      stripe/route.ts         POST   - Stripe webhook
      github/route.ts         POST   - GitHub webhook