def build_agg_tooltip(hover_text=None, agg_text=None, aggregated_col=None):
    """Produce a consistent tooltip based on available chart configuration.

    Args:
        hover_text (str, optional): the desired label for the value to be shown in the
            tooltip
        agg_text (str, optional): any aggregation text used for the chart
        aggregated_col (str, optional): any column name used for aggregation

    Returns:
        tuple(str, str): a single tooltip

    """
    if hover_text is None:
        if agg_text is None:
            if isinstance(aggregated_col, str):
                hover_text = aggregated_col
            else:
                hover_text = 'value'
        else:
            hover_text = agg_text
            if isinstance(aggregated_col, str):
                hover_text = '%s of %s' % (hover_text, aggregated_col)

    return hover_text.title(), "@values"