Is it possible to run the tool to only just look for potential issues it can fix but not actually have the tool resolve them?
I am keen to know what it finds.
Is there any way to know what sfcfix actually does? Is the source code available anywhere?
Without a script .... in which case it performs a number of pre-determined processes.
With a script .... in which case it processes the instructions provided in the script.
.... there is no scan only mode.
In "auto" mode essentially it looks in your CBS.log for a recent run of SFC and if one is not present it will instigate a SFC scan. Any corruptions that SFC cannot repair will be logged so that replacements can be provided manually.
Just to add to what @Gary R has correctly mentioned, SFCFix is not a diagnostics tool, it's designed for WU helpers like myself and Gary to perform fixes in a safe and efficient manner. The source code is private for obvious reasons and I would strongly recommend that you don't attempt to write any SFCFix scripts either because the tool will not hesitate to run it.