While it is ideal to respond with a bare minimum and still get full marks, if you have doubts over whether your succinct response would get full marks then contrary to what others believe, I would probably recommend that you write as much relevent information as you can when answering a question, unless otherwise specified [e.g. they ask you to specifically name ONE idea instead of two]. I would recommend this especially for longer responses worth several marks.
Just make sure that they are relevent ideas that answer the question. This allows the marker to see your depth of knowledge and understanding and shows that you are not rote learning the course. Generally you would have no idea what's expected of you in the marking criteria and from personal experience, writing as many relevent points as you can will give you more chances to fulfill the marking criteria. The only exception would probably be extended responses (e.g. essays, creative writing...) where the response is assessed as a whole for its quality.
Also, I know in the HSC at least, (after hearing from HSC markers themselves) even if you do write irrelevent points, no marks would be deducted unless these points are incorrect or are self-contradicting. The only detriment of doing this is the potential of wasting time.
