api-documentation

API Documentation

Best practices for documenting APIs and code interfaces. Eliminates ~100-150 lines of redundant documentation guidance per agent.

Core Documentation Principles

1. Document the why, not just the what - Explain intent and rationale
2. Keep docs close to code - Inline documentation stays synchronized
3. Document contracts, not implementation - Focus on behavior
4. Examples are essential - Show real usage
5. Update docs with code - Outdated docs are worse than no docs

Function/Method Documentation

Python (Docstrings)

def calculate_discount(price: float, discount_percent: float) -> float:
    """
    Calculate discounted price with percentage off.

    Args:
        price: Original price in dollars (must be positive)
        discount_percent: Discount percentage (0-100)

    Returns:
        Final price after discount, rounded to 2 decimals

    Raises:
        ValueError: If price is negative or discount > 100

    Examples:
        >>> calculate_discount(100.0, 20.0)
        80.0
        >>> calculate_discount(50.0, 50.0)
        25.0

    Note:
        Discount percent is capped at 100% (minimum price of 0)
    """
    if price < 0:
        raise ValueError("Price cannot be negative")
    if discount_percent > 100:
        raise ValueError("Discount cannot exceed 100%")

    discount_amount = price * (discount_percent / 100)
    return round(price - discount_amount, 2)

JavaScript (JSDoc)

/**
 * Calculate discounted price with percentage off
 *
 * @param {number} price - Original price in dollars (must be positive)
 * @param {number} discountPercent - Discount percentage (0-100)
 * @returns {number} Final price after discount, rounded to 2 decimals
 * @throws {Error} If price is negative or discount > 100
 *
 * @example
 * calculateDiscount(100.0, 20.0)
 * // returns 80.0
 *
 * @example
 * calculateDiscount(50.0, 50.0)
 * // returns 25.0
 */
function calculateDiscount(price, discountPercent) {
  if (price < 0) {
    throw new Error('Price cannot be negative');
  }
  if (discountPercent > 100) {
    throw new Error('Discount cannot exceed 100%');
  }

  const discountAmount = price * (discountPercent / 100);
  return Math.round((price - discountAmount) * 100) / 100;
}