Developed for the ARGUGRID project, MARGO implements an argumentation framework for practical reasoning. A logic language is used as a concrete data structure for holding statements representing knowledge, goals, and decisions of an agent. Different qualitative and quantitative priorities are attached to these items, corresponding to the probability of the knowledge, the preferences between goals, and the expected utilities of decisions. These concrete data structures consist of information providing the backbone of arguments. Due to the abductive nature of decision making, we built arguments by reasoning backwards, possibly by making suppositions. Moreover, arguments are defined as tree-like structures. In this way, MARGO evaluates the possible decisions, suggests some solutions, and provides an interactive and intelligible explanation of the choice made.