A first network device executing a device simulation tool receives a selection of a second network device in a communications network. The first network device receives a selection of at least one use case, scenario or error condition associated with operation of the second network device or the communications network, and executes a network simulation of the communications network based on the at least one use case, scenario or error condition. The first network device generates a call flow diagram, which involves the selected second network device, based on the executed network simulation, and provides a graphical display of the generated call flow diagram.