What do we want from this prediction tool?

Usually, we want a tool  which  helps  rule in or rule out an event, or determine  the probability of the event.  Thus, we are usually interested in the accuracy of the tool and our test related outcomes of interest are sensitivity, specificity, predictive values and likelihood ratios.

Don't confuse this terminology with clinical outcomes, which are  what we  ultimately need to understand.  Unfortunately few decision aids have been evaluated for their effect on clinical outcome. 

If we are interested in the effect of a decision tool on higher outcomes,  then we would search for  test related outcomes such as  mortality and cost effectiveness: here the test related outcome and clinical outcome are the same.