API Documentation Generator

Target: $0

Format: $1 (default: markdown)

Steps

1. Discover endpoints — Scan route files:

   • Next.js App Router: app/api/**/route.ts
   • Express/Fastify: routes/**/*.ts
   • Read each handler to extract HTTP methods

2. For each endpoint, extract:

   • HTTP method and path
   • Request body schema (from Zod schemas or TypeScript types)
   • Query parameters
   • Path parameters
   • Response shape (from return statements or response types)
   • Auth requirements (middleware, decorators, session checks)
   • Error responses (from error handling code)

3. Group endpoints by resource or feature area

4. Generate documentation:

Markdown format

# API Reference

## Authentication

All endpoints except those marked "Public" require a valid session cookie or Bearer token.

---

## Users

### GET /api/users

Retrieve a list of users.

**Auth**: Admin only

**Query Parameters**:
| Param | Type | Required | Default | Description |
|-------|------|----------|---------|-------------|
| page | number | no | 1 | Page number |
| limit | number | no | 20 | Items per page |

**Response** `200 OK`:
\`\`\`json
{
  "users": [{ "id": "...", "name": "...", "email": "..." }],
  "total": 100,
  "page": 1
}
\`\`\`

**Errors**:
| Status | Code | Description |
|--------|------|-------------|
| 401 | UNAUTHORIZED | Missing or invalid session |
| 403 | FORBIDDEN | Not an admin |

OpenAPI format

Generate a valid OpenAPI 3.0 YAML document with:

• Info block (title, version, description)
• Server URLs
• Paths with operations
• Component schemas (reusable request/response types)
• Security schemes

5. Verify completeness — Cross-reference discovered endpoints with the route file tree to ensure nothing was missed.

Output Format

• Markdown: single docs/api.md file or per-resource files
• OpenAPI: openapi.yaml at project root

Constraints

• Document what exists, don't invent endpoints
• Extract schemas from code (Zod, TypeScript types), don't guess
• Include error responses — they're as important as success responses
• Keep examples realistic (use plausible data, not "string" or "123")
• If auth middleware exists, check which endpoints use it