Webel: Mathematica: A help Rule 'rule$arg' for an '$arg$' (argument) accepts keys: '$k$help' (required), '$k$def' (required if $k$req = True not given), '$k$req' (True if $k$def not given), '$k$warn', '$k$tip', '$k$lab', '$k$type', '$k$mult' and '$k$pat'
Webel: Mathematica: CONVENTION: An '$opt$' (option) or '$arg$ (argument) help holder may be have an associated (typically short) '$lab$opt$' or '$lab$arg$' label help holder for use in GUIs and views.
Webel: Mathematica: CONVENTION: "pattern helpers" (which are not themselves Patterns) use the prefix '$pat$. Encapsulated Patterns use a 'pat$' prefix, and may use a '$pat$' pattern helper (such as an Alternatives).
Webel: Mathematica: CONVENTION: Argument help holders use a String variable with the prefix '$arg$', a related '$info$arg$' String, a 'def$arg$' default value expression and/or 'req$arg$', and optional '$warn$arg$', '$tip$arg$, '$lab$arg$', 'type$arg$'..
