As a licensed engineer, my view has always been 'stick it in the book'.
If it's a minor defect of no consequence '...nosewheel appears dusty...' I can always fix it/pen it off.
If I can't fix it, pen it or ADD it, then it should quite righty ground the aircraft.
The rule of thumb I always use with defects is 'would I let my kids fly on this aircraft?' Of course that rule does cause problems as they grow up to be teenagers...