The ability to trigger scripts (including passing in variables and parameters) via the FMP URL has been a great addition to the developers' bag of tricks for doing cool interactive stuff with webviewers.
My understanding is that this is possible only within FMGo and within FMP files which are hosted.
It would be great to have this possible also for standalone, non-hosted, FMP files.
It's certainly possible to use Open URL with the "fmp://" prefix in FM Pro, not just Go.
Additionally, you can open non-hosted fmp files using the "file://" prefix, but you can't run scripts.
How this step is handled depends on part on your default browser settings (if I drop fmp:// into Chrome it doesn't work, but in Firefox it does).