Hono API Scaffolder Skill

Hono API Scaffolder

Add structured API routes to an existing Cloudflare Workers project. This skill runs AFTER the project shell exists (via cloudflare-worker-builder or vite-flare-starter) and produces route files, middleware, and endpoint documentation.

Workflow

Step 1: Gather Endpoints

Determine what the API needs. Either ask the user or infer from the project description. Group endpoints by resource:

Users:    GET /api/users, GET /api/users/:id, POST /api/users, PUT /api/users/:id, DELETE /api/users/:id
Posts:    GET /api/posts, GET /api/posts/:id, POST /api/posts, PUT /api/posts/:id
Auth:     POST /api/auth/login, POST /api/auth/logout, GET /api/auth/me

Step 2: Create Route Files

One file per resource group. Use the template from assets/route-template.ts:

// src/routes/users.ts
import { Hono } from 'hono'
import { zValidator } from '@hono/zod-validator'
import { z } from 'zod'
import type { Env } from '../types'

const app = new Hono<{ Bindings: Env }>()

// GET /api/users
app.get('/', async (c) => {
  const db = c.env.DB
  const { results } = await db.prepare('SELECT * FROM users').all()
  return c.json({ users: results })
})

// GET /api/users/:id
app.get('/:id', async (c) => {
  const id = c.req.param('id')
  const user = await db.prepare('SELECT * FROM users WHERE id = ?').bind(id).first()
  if (!user) return c.json({ error: 'Not found' }, 404)
  return c.json({ user })
})

// POST /api/users
const createUserSchema = z.object({
  name: z.string().min(1),
  email: z.string().email(),
})

app.post('/', zValidator('json', createUserSchema), async (c) => {
  const body = c.req.valid('json')
  // ... insert logic
  return c.json({ user }, 201)
})

export default app

Step 3: Add Middleware

Based on project needs, add from assets/middleware-template.ts:

Auth middleware — protect routes requiring authentication:

import { createMiddleware } from 'hono/factory'
import type { Env } from '../types'

export const requireAuth = createMiddleware<{ Bindings: Env }>(async (c, next) => {
  const token = c.req.header('Authorization')?.replace('Bearer ', '')
  if (!token) return c.json({ error: 'Unauthorized' }, 401)
  // Validate token...
  await next()
})

CORS — use Hono's built-in:

import { cors } from 'hono/cors'
app.use('/api/*', cors({ origin: ['https://example.com'] }))

Step 4: Wire Routes

Mount all route groups in the main entry point:

// src/index.ts
import { Hono } from 'hono'
import type { Env } from './types'
import users from './routes/users'
import posts from './routes/posts'
import auth from './routes/auth'
import { errorHandler } from './middleware/error-handler'

const app = new Hono<{ Bindings: Env }>()

// Global error handler
app.onError(errorHandler)

// Mount routes
app.route('/api/users', users)
app.route('/api/posts', posts)
app.route('/api/auth', auth)

// Health check
app.get('/api/health', (c) => c.json({ status: 'ok' }))

export default app

Step 5: Create Types

// src/types.ts
export interface Env {
  DB: D1Database
  KV: KVNamespace      // if needed
  R2: R2Bucket         // if needed
  API_SECRET: string   // secrets
}

Step 6: Generate API_ENDPOINTS.md

Document all endpoints. See references/endpoint-docs-template.md for the format:

## POST /api/users
Create a new user.
- **Auth**: Required (Bearer token)
- **Body**: `{ name: string, email: string }`
- **Response 201**: `{ user: User }`
- **Response 400**: `{ error: string, details: ZodError }`

Key Patterns

Zod Validation

Always validate request bodies with @hono/zod-validator:

import { zValidator } from '@hono/zod-validator'
app.post('/', zValidator('json', schema), async (c) => {
  const body = c.req.valid('json')  // fully typed
})

Install: pnpm add @hono/zod-validator zod

Error Handling

Use the standard error handler from assets/error-handler.ts:

export const errorHandler = (err: Error, c: Context) => {
  console.error(err)
  return c.json({ error: err.message }, 500)
}

API routes must return JSON errors, not redirects. fetch() follows redirects silently, then the client tries to parse HTML as JSON.

RPC Type Safety

For end-to-end type safety between Worker and client:

// Worker: export the app type
export type AppType = typeof app

// Client: use hc (Hono Client)
import { hc } from 'hono/client'
import type { AppType } from '../worker/src/index'

const client = hc<AppType>('https://api.example.com')
const res = await client.api.users.$get()  // fully typed

Route Groups vs Single File

| Project size | Structure | |-------------|-----------| | < 10 endpoints | Single index.ts with all routes | | 10-30 endpoints | Route files per resource (routes/users.ts) | | 30+ endpoints | Route files + shared middleware + typed context |

Reference Files

| When | Read | |------|------| | Hono patterns, middleware, RPC | references/hono-patterns.md | | API_ENDPOINTS.md format | references/endpoint-docs-template.md |

Assets

| File | Purpose | |------|---------| | assets/route-template.ts | Starter route file with CRUD + Zod | | assets/middleware-template.ts | Auth middleware template | | assets/error-handler.ts | Standard JSON error handler |

Agent Skills: Hono API Scaffolder

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Skill Files