Brush Needs Size - Inexcusable Design Flaw
It is absolutely unacceptable that the brush tool does not have a size setting.
It is straightforward to change the path size after drawing, it should be straightforward to set what path size is drawn.
This is not a feature request. This is a BASIC CORE APPLICATION FAILURE. Whoever neglected to add size should be fired and prevented from ever designing an application again.
WHAT WERE YOU THINKING?
Asher, welcome to UV. This is exactly the place to rage about stupid bugs. But you should tell a bit more about that size problem.
As Lance says below, the size of a brush is controlled with the Weight parameter in the Stroke panel (or Control, or Properties, it depend on what part of UI you have enabled).
Yes, this parameter can’t be set directly in the Brushes panel. Yes, sometimes if a brush stroke is really fat, it does not correspond that weight at all.
'One point' here means 'one original width of a stroke'. While it’s commonly known agreement, I personally find it confusing, and even made a separate (wonky) request to rethink that — https://illustrator.uservoice.com/forums/333657-illustrator-feature-requests/suggestions/33386008-art-brushes-different-weight-value
But what did you mean?
That's because the brush in illustrator creates a stroked path. The size is set with the stroke width. You can set the stroke width before you draw a stroked path with the brush.
This is how the brush tool has always functioned in Illustrator.