The purpose of the paper is to show that management tools have a dual dimension: they simultaneously constrain and empower people. To demonstrate this paradox, this article refers to studies from the research stream founded by Michel Foucault that highlight the mechanisms that enable control tools to constrain people. The link between knowledge and power plays a major part in this dynamic. This article links such research to that of Armand Hatchuel. Hatchuel extended the idea of the relationship between knowledge and power by showing that knowledge has two faces: it constrains, but through its reflexive dimension it also empowers employees. Knowledge enablesindividuals to develop new behaviors that they themselves define. On this conceptual basis, our article underlines that control tools contain both the dimensions of constraint and of empowerment. We compare two case studies that demonstrate this dual dimension. The data was collected longitudinally using observations, semi-directive interviews and documentary data. The first case study shows that a tool for competence evaluation, initially designed with a view to empowerment, also contains a dynamic of constraint. The use of this empowering tool produces new knowledge that transforms it such that it becomes more constraining. Conversely, the second case study shows how a satisfaction survey, originally directed towards constraint, produces new knowledge that empowers employees, enabling them to adopt new behaviors. This article shows that the dimensions of constraint and empowerment are present simultaneously in control mechanisms. These two dimensions should not be opposed; they co-exist. Analyzing the complexities of how they are related should enable managers as well as researchers to better understand the processes of setting up and transforming such control mechanisms