Macro scripts structure collaborative learning and foster the emergence of knowledge-productive interactions such as argumentation, explanations and mutual regulation. We propose a pedagogical model for the designing of scripts and illustrate this model using three scripts. In brief, a script disturbs the natural convergence of a team and in doing so increases the intensity of interaction required between team members for the completion of their collaborative task. The nature of the perturbation determines the types of interactions that are necessary for overcoming it: for instance, if a script provides students with conflicting evidence, more argumentation is required before students can reach an agreement. Tools for authoring scripts manipulate abstract representations of the script components and the mechanisms that relate components to one another. These mechanisms are encompassed in the transformation of data structures (social structure, resources structure and products structure) between script phases. We describe how this pedagogical design model is translated into computational structures in three illustrated scripts.