HI. The question should be: "How do you decribe a person who does not like to speak much, but is not shy?
A person could be described as one of the following:
'laid back' - relaxed
impassive' - not getting involved
'succinct'. - able to make their point with only a few words.
'laconic' - similar to succinct - brief and to the point.
'tight-lipped', - secretive
'Hidden depths' - Seems quiet but has hidden attributes