The Evolutionary Requirements Analyser (ERA) applies evolutionary computing techniques to automatically select optimal combinations of human and machine agents in a system model to match non-functional requirements (NFRs). The tool assesses the reliability, performance times and cost of different system models by executing many model variants, as evolving forms, with scenarios and different combinations of environmental variables. Better performing models are selected, to converge on an optimal solution. Use of the tool is illustrated with a case study of requirements analysis for component selection in a command and control system.