I am the author of Serial Chinese Room, Interprocess, and Telemetry (SCRIPT) Script (Script2) and the Kabuki Starship GitHub open-source organization. I have an SDK, ScriptTek that I’m doing a hybrid mbed or Arduino firmware SDK, and a Kabuki Toolkit app SDK both based on Script2. I use inline header files, of which the standard is inl file, because on some compilers they will demand you use an include once guard on the header, but if you inl files then the compiler won’t bark at you. I really shouldn’t have to rename my inl files to make them work on the mbed online IDE. You can use the extension with the offline mbed API. If possible, the inl extension should be added to the list of accepted file extensions for the mbed online IDE.