It seems that currently the only public way to create an EdmFunction is to use the static Create method (both constructors are internal). The Create method however will set the whole function and it is parameters as read only (i.e. it calls function.SetReadOnly() before returning it). Give that, there are no valid public surface scenarios for invoking the AddParameter method.
Comments: This method is useable from a custom model convention.
Comments: This method is useable from a custom model convention.