1. CHECK PREREQUISITES → Verify design exists if Medium+
2. APPLY STANDARDS → Type hints, docstrings, naming
3. IMPLEMENT → Write code following patterns
4. VALIDATE → Run validate_structure.py
5. SECURE → Use securing-code skill before delivery

# RIGHT - Imports at the top, organized
"""Module docstring."""
from __future__ import annotations

import os
import sys
from typing import Protocol

from third_party import SomeClass

from myproject.domain import Entity


def my_function():
    ...

# WRONG - Imports scattered in code
def process_data():
    import json  # NEVER import inside functions
    ...

def another_function():
    try:
        from module import thing  # NEVER import inside try/except
    except ImportError:
        thing = None

# WRONG
def process(data):
    return data.upper()

# RIGHT
def process(data: str) -> str:
    return data.upper()

def calculate_total(items: list[LineItem], tax_rate: Decimal) -> Money:
    """Calculate order total including tax.

    Args:
        items: Line items with price and quantity
        tax_rate: Tax rate as decimal (0.21 for 21%)

    Returns:
        Total amount as Money value object

    Raises:
        InvalidTaxRateError: If tax_rate is negative
    """

# WRONG - Silent failure
def get_user(user_id: str) -> User | None:
    user = db.find(user_id)
    return user  # Caller might forget to check None

# RIGHT - Explicit failure
def get_user(user_id: str) -> User:
    user = db.find(user_id)
    if not user:
        raise UserNotFoundError(f"User {user_id} not found")
    return user

python scripts/validate_structure.py generated_file.py

"""
Module docstring explaining purpose.
"""
from __future__ import annotations

from typing import Protocol
from dataclasses import dataclass

# Interfaces first
class IRepository(Protocol):
    ...

# Value Objects
@dataclass(frozen=True)
class Money:
    ...

# Domain classes
class Service:
    ...