Simulating agile processes prior to adoption can reduce the risk of enacting an ill-fitting process. Agent-based simulation is wellsuited to capture the individual decision-making valued in agile. Yet, agile's lightweight nature creates simulation difficulties as agents must fill-in gaps within the specified process. Deliberative agents can do this given a suitable planning domain model. However, no such model, nor guidance for creating one, currently exists. In this work, we propose a means for constructing an agile planning domain model suitable for agent-based simulation. As such, the domain model must ensure that all activity sequences derived from the model are executable by a software agent. We prescribe iterative elaboration and decomposition of an existing process to generate successive internally-complete and-consistent domain models, thereby ensuring plans derived from the model are valid. We then demonstrate how to generate a domain model and exemplify its use in planning the actions of a single agent.