They overlap. My bandsaw is a tool and a toy.
Cars are often toys, but almost always tools.
A nuclear reactor is something that would have a very low "toyness" score, i.e. you wouldn't "play" with it.
A plastic toy car would have a very high "toyness" score, as it is literally designed to play with (by kids).
I kind of fear my analogy of two different dimensions breaks down here because I'm left wondering what things would have a low "toolness" score ...
Maybe expressing it as a complex number would help, eg. toolness + i(toyness)
In polar form a low angle would indicate a high "toolness to toyness" ratio.
"Toolness" is, at least to a large extent, a synonym for "(practical) utility".
Code, for example, can be played with but can also deliver significant impact to a large group of people.
A toy car, as another example, can be played with but delivers value to only one person at once (well, depending on how you use it).
Haute couture fashion?