Not sure if this is actually a bug or just something really weird in my installation.
The attached file shows a shapefile of Scotland where I am trying to use the simplify polygon tool, which requires a parameter for the simplification tolerance. The Simplify Polygon tool window does not have an input box for that specific parameter, just the input box label?
Therefore because the simplification tolerance is required (obviously), the tool will not work from the toolbox.
Using ArcGIS 10.2.2 version: 10.2.2.3552
cool... this old thread bubbles forth...
and fixed in arcmap 10.3
That's why my screen shot for 10.4 showed all was right in that version
So there you have it... closure on an ancient problem