Correct UML diagram

If you take a UML book and as you go on reading, you will get to a point where the author says something like .. "Hey, it is upto you to decide what to draw in order to communicate your solution with the concerned parties." Often in practice however, the concerned parties in our equation are the ones requesting for a specific diagram. This may not sound like a problem but on on one such instance a fellow team member was asked to present a class diagram for a batch processing application when in fact a combination of class diagram and either a sequence diagram or an activity diagram with less emphasis on the class diagram would present a clearer window to visualizing the solution. Of course, it might have been just a figure of speech.. "I need a class diagram.. meaning some sort of diagram.. for me to understand what you've been upto."