Hello Vincent, I think I was unclear in my (hasty) mail.
Take for example the command "\newcommand" (12. definitions) @item cmd Required; @code{\@var{cmd}} is the command name. For @code{\newcommand}, it must not be already defined and must not begin with @code{\end}. For @code{\renewcommand}, it must already be defined. @item nargs Optional; an integer from 0 to 9, specifying the number of arguments that the command will take. If this argument is not present, the default is for the command to have no arguments. When redefining a command, the new version can have a different number of arguments than the old version. I am unable to take from the texi file that "nargs" is optional. It is written there, but it is not extractable. This is the kind of information I'd like to include in ltxref.org Patrick