I know that this is old but
tool/to?ol/
Noun:
A device or implement, esp. one held in the hand, used to carry out a particular function.
I don’t believe that a yoga mat falls in that category. If it does then any thing that has a use is a tool so if i use my brother to lift me up over the fence he is a tool. If I use my Rebbi to learn Torah then my Rebbi is a tool. Btw that is where the slang comes from.