King will take charge of his first full international match when Ireland face Germany on Friday, having assumed temporary control of the senior team following Giovanni Trapattoni's departure last month.
"They are not here just to come and have a trip," PA quotes King as saying.
"Everybody who is there is there for a reason, and whether that reason is a full 90 minutes, a half performance, a game against Kazakhstan, a half game against Kazakhstan, a half game against Germany, that will unfold. I don't know yet, but that's why we have the squad."
Ireland are currently six points behind second-placed Sweden with two games left, although their inferior goal difference means that qualification for next year's World Cup is out of reach.