Microsoft Research Detours - Detours is a software package for re-routing Win32 APIs underneath applications.
Postman - The Collaboration Platform for API Development
EasyHook - The reinvention of Windows API Hooking
Insomnia REST - The most intuitive cross-platform REST API Client ð´
WinAPIOverride - WinAPIOverride : This software allows you to monitor and/or modify any function of a process for any calling convention (stdcall or cdecl)
soapUI - SoapUI Pro is one of the most prominent API testing platforms around, allowing developers to quickly prototype the functions of their apps and get them to market with little hassle.