API Documentation Generator

Generate comprehensive API documentation by analyzing source code. Extracts endpoints, parameters, request/response schemas, authentication requirements, and generates examples. Works with Express, FastAPI, Django REST Framework, Rails, Spring Boot, and other frameworks.

Usage

"Generate API docs from my Express app"
"Create API reference documentation"
"Document all endpoints in this project"
"Generate OpenAPI spec from my code"

How It Works

1. Framework Detection

# Detect framework from dependencies
cat package.json 2>/dev/null | python3 -c "
import json,sys
d=json.load(sys.stdin).get('dependencies',{})
for fw in ['express','fastify','koa','hapi','nestjs','next']:
    if fw in str(d): print(f'Node: {fw}')
" 2>/dev/null

cat requirements.txt setup.py pyproject.toml 2>/dev/null | grep -i "fastapi\|django\|flask\|starlette"

2. Endpoint Extraction

Scan source code for route definitions:

Express/Node:

grep -rn "router\.\(get\|post\|put\|patch\|delete\|all\)\|app\.\(get\|post\|put\|patch\|delete\)" src/ routes/

FastAPI/Python:

grep -rn "@app\.\(get\|post\|put\|patch\|delete\)\|@router\.\(get\|post\|put\|patch\|delete\)" src/ app/

Django REST Framework:

grep -rn "class.*ViewSet\|class.*APIView\|path(" */views.py */urls.py

For each endpoint, extract:

• HTTP method and path
• URL parameters and query parameters
• Request body schema (from TypeScript types, Pydantic models, serializers)
• Response format and status codes
• Authentication requirements
• Middleware chain
• Rate limiting rules

3. Schema Extraction

Analyze types/models for request/response schemas:

• TypeScript interfaces and types
• Pydantic models with field validators
• Django serializers with field definitions
• Joi/Zod validation schemas
• JSON Schema definitions

4. Example Generation

Generate realistic request/response examples:

• Valid request with all required fields
• Response with realistic data
• Error response examples (400, 401, 403, 404, 500)
• Curl command for quick testing
• SDK examples in popular languages

5. Documentation Output

Generate in multiple formats:

Markdown API Reference:

## POST /api/users

Create a new user account.

**Authentication:** Bearer token required
**Rate limit:** 10 requests/minute

### Request Body
| Field | Type | Required | Description |
|-------|------|----------|-------------|
| email | string | yes | Valid email address |
| name | string | yes | Full name (2-100 chars) |
| role | enum | no | "user" or "admin" (default: "user") |

### Response (201 Created)
```json
{
  "id": "usr_abc123",
  "email": "user@example.com",
  "name": "Jane Smith",
  "role": "user",
  "createdAt": "2026-04-30T10:00:00Z"
}

Errors

• 400 — Invalid email format or missing required field
• 409 — Email already registered
• 429 — Rate limit exceeded

**OpenAPI 3.1 spec** — machine-readable for Swagger UI, Redoc, Postman

### 6. Completeness Check

Verify documentation quality:
- All endpoints documented
- All parameters described
- Response schemas match actual responses
- Authentication documented
- Error codes listed
- Examples present and valid

## Output

API Documentation Generated

Framework: Express.js + TypeScript Endpoints found: 23 Documentation completeness: 87%

Generated Files

• docs/api-reference.md (full markdown reference)
• docs/openapi.yaml (OpenAPI 3.1 spec)
• docs/examples/ (curl examples per endpoint)

Coverage

Undocumented

• PATCH /api/users/:id — has route but no type annotations
• POST /api/webhooks/stripe — raw req.body, no schema