This paper presents the approach to ontology development that is part of the Disciple-LAS shell and methodology for the building of knowledge-based agents. A characteristic feature of this approach is that a detailed specification of the ontology to be developed results from a conceptual modeling of the application domain of the knowledge-based agent to be built. This specification guides the process of building the ontology which consists in importing knowledge from external knowledge servers, and in using the ontology building tools of Disciple. Knowledge import and reuse are facilitated by the fact that the representation of the ontology is based on the OKBC knowledge model. This approach is used to develop an ontology for an agent that critiques military courses of actions.