Microservices　is　a　crucial　architecture　design　pattern　for　developing　cloud-native　applications,　which　focuses　on　decomposing　a　large　and　complex　software　system　into　autonomous　components　that　can　be　independently　developed　and　deployed.　However,　microservices　design　is　not　a　trivial　task,　which　highly　depends　on　the　profound　knowledge　and　experience　of　system　design　and　target　domain.　This　is　a　challenge　for　novice　software　architects.　In　this　paper,　we　propose　a　microservices　design　tool　named　RapidMS,　which　only　requires　architects　to　specify　potential　context　boundaries　on　the　requirements　model.　The　microservices　architecture　design　model　with　component　structure　and　interaction　views　can　be　automatically　generated　without　extra　human　effort.　Moreover,　the　proposed　tool　can　automatically　calculate　the　characteristic　metrics　of　the　microservices,　which　indicate　the　quality　of　the　different　aspects　of　models　to　support　rapid　architecture　refinements.　We　demonstrate　the　tool＇s　effectiveness　through　five　case　studies.　The　experimental　result　shows　that　architects　can　get　better　decomposition　of　requirement　model　within　four　iterations　and　over　90%　of　microservice　architecture　diagrams　can　be　correctly　generated　within　10　seconds.　RapidMS　can　be　further　extended　and　applied　in　the　software　industry　to　reduce　the　cost　and　difficulty　of　microservices　decomposition　and　design.　The　tool　can　be　downloaded　at　https://rm2pt.com/advs/rapidms,　and　a　demo　video　casting　its　features　is　at　https:　//youtu.be/AoIM41FTnF0