from typing import Dict


def format_error(status: int, description: str) -> Dict[str, str]:
    """
    Uniform error format for API responses.

    :param status: the error status code
    :param description: the error description
    :return: a dictionary describing the error
    """
    errors = {
        400: 'Bad Request',
        401: 'Unauthorized',
        404: 'Not Found',
        500: 'Internal Server Error'
    }
    return {'error': errors.get(status) or '(undefined)',
            'error_description': description}