Prototyping is an effective and efficient way of requirements validation to avoid introducing errors in the early stage of software development. Our previous work presents a tool RM2PT to automatically generate prototypes from requirements models. The stakeholders can easily check whether the requirements reflect their real needs by investigating the executions of use cases in the generated prototypes. However, the conflict and contradictory of the requirements are hard to be discovered. In this paper, we enhance RM2PT by introducing consistency checking and state observations in the generated prototypes. Requirements inconsistency can be automatically detected and further fixed through carefully analyzing the contracts of system operations and system state observations. We have conducted four case studies with over 50 use cases. The experimental result shows that 107 requirements inconsistency are founded in requirements validations. Overall, the result is satisfiable, and the enhanced RM2PT can be further applied to the software industry for requirements validation. The tool can be downloaded at http://rm2pt.mydreamy.net and a demo video casting its features is at https://youtu.be/Y7GNa57WGfA.