I don't really know what a uwp app is (I'm stuck on Windows 7 everywhere). But if it connects to the puck via the UART service, you can probably just send strings. Terminate each line with a \n as if you were hitting enter after each line.
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
I don't really know what a uwp app is (I'm stuck on Windows 7 everywhere). But if it connects to the puck via the UART service, you can probably just send strings. Terminate each line with a \n as if you were hitting enter after each line.