@favancini, with the original TRIGGERcmd or TRIGGER command google assistant action, the format of the voice commands are like this: "Hey Google, ask TRIGGERcmd (or TRIGGER command) to run X with parameter Y"
So you could say something like this:
"Hey Google, ask TRIGGERcmd to run album with parameter X." Where X is the name of your playlist.
Your command could run a script that runs your Mp3 player with X as your playlist parameter.