A few years ago, my friend, a GM of a MLB team and I discussed a Minor League player who displayed strong numbers. I ask "why is he not in the Major Leagues"? Let us look at the "book", which displayed the players strong and weak points [5 tools] and his 6th Tool.
MLB Scouts, College Coaches, Summer Team coaches, HS coaches all have an informal "book". Depending on the quality of the reporter's the "book" may have specific accuracy's. It is a opinion, a judgement and prediction for the player's future success. For a HS players entering College, the College Coaches "book" would be very interesting.
However, if a player can review it would provide motivation for the player to improve his skills "off and on" the field.
One year, our American team traveled to Japan with two ex-Dodgers outfielders as our Coaches.
They recalled that at the "cut down" time in Spring Training, Tommy would call each at a separate time into his office.
Tommy said "if we keep 25 players" I would keep you, however I have to send you to Triple A.
In Japan, they each said that what Tommy told him.
The Dodger's "book" indicated each a 4th or 5th outfielder on a ML roster.