def generateOperation(length: int, amount: float) -> str:
    """
    Generate an operation (operation = creation of a virtual credit card)

    :param length: The duration of the virtual credit card in months
    :type length: int
    :param amount: The amount in Euros contained in the virtual credit card
    :type amount: float
    :return: A string describing the virtual credit card / the operation
    :rtype: str
    """
    return ("{\"duree\":" + str(length) +
            ",\"mntSaisi\":" + str(amount) + "}")