By "tool" blocks, I mean the blocks you receive from pressing "import tools" in the file dropdown menu.
I was wondering what the 
block does. What it seems to do is report the value of the parameter, but wouldn't that be the same as using the parameter itself? There seems to be no help image about it.
My guess is that you can use it to drop it in dropdown inputs, such as this one:
It can also be used to quickly create the identity function, or a constant function that always reports the same value.
... and you can use it to put a non-numeric string in a numeric input slot. Useful for NaN or ∞, or especially for exact rationals and complex numbers if you load the bignum library.
P.S. Thanks for reminding me to add a help screen for it!