A property which appears as a tooltip

I would like to be able to define a block property which is hidden and only appears as a tool tip when I hover over the block.

I imagine that this property might be called prompt or tooltip. Alternatively there could be a tag (ie. #.hover.description) which makes the existing description property display as a tooltip.

Just to make it concrete, in this image I’d want the prompt tag to only display on hover. If there’s an existing way to achieve this in my settings, that would be great too.

ps. I looked at the block-hidden-properties setting, but it seems to make it so that I cannot even find the property anymore.