Just recounting a story as a story, i.e. telling the reader what happens, is never appropriate for an academic essay. An academic essay uses elements of the story to illustrate broader points. For example, if the essay question is about the aims of the Spartan wars, you might talk about why Agesilaus sacrificed at Aulis, but would not simply state that he had, or tell us how he did it or what happened during the sacrifice. In other words, always use events to underpin or prove a point: never simply list them to pad out your essay.