I took an online Myers-Briggs personality test and i'm an an INTJ.
The Portait of the Mastermind (INTJ)
Of the four aspects of strategic analysis and definition, it is the contingency planning or entailment organizing role that reaches the highest development in Masterminds. Entailing or contingency planning is not an informative activity, rather it is a directive one in which the planner tells others what to do and in what order to do it. As the organizing capabilities the Masterminds increase so does their inclination to take charge of whatever is going on.
It is in their abilities that Masterminds differ from the other Rationals, while in most of their attitudes they are just like the others. However there is one attitude that sets them apart from other Rationals: they tend to be much more self-confident than the rest, having, for obscure reasons, developed a very strong will. They are rather rare, comprising no more than, say, one percent of the population. Being very judicious, decisions come naturally to them; indeed, they can hardly rest until they have things settled, decided, and set. They are the people who are able to formulate coherent and comprehensive contingency plans, hence contingency organizers or "entailers."
Masterminds will adopt ideas only if they are useful, which is to say if they work efficiently toward accomplishing the Mastermind's well-defined goals. Natural leaders, Masterminds are not at all eager to take command of projects or groups, preferring to stay in the background until others demonstrate their inability to lead. Once in charge, however, Masterminds are the supreme pragmatists, seeing reality as a crucible for refining their strategies for goal-directed action. In a sense, Masterminds approach reality as they would a giant chess board, always seeking strategies that have a high payoff, and always devising contingency plans in case of error or adversity. To the Mastermind, organizational structure and operational procedures are never arbitrary, never set in concrete, but are quite malleable and can be changed, improved, streamlined. In their drive for efficient action, Masterminds are the most open-minded of all the types. No idea is too far-fetched to be entertained-if it is useful. Masterminds are natural brainstormers, always open to new concepts and, in fact, aggressively seeking them. They are also alert to the consequences of applying new ideas or positions. Theories which cannot be made to work are quickly discarded by the Masterminds. On the other hand, Masterminds can be quite ruthless in implementing effective ideas, seldom counting personal cost in terms of time and energy.
also, check out this link for another discription, which is a bit more detailed. http://typelogic.com/intj.html