method_format / atom_setformat

Hi !

ive reached the point where i would like to provide arguments though sprintf like formatting . with these functions :

atom_setformat(long *ac, t_atom **av, C74_CONST char *format,...);

object_method_format(t_object *x, t_symbol *s, t_atom *rv, C74_CONST char *format,...);

unfortunately it seem not to be working using sprintf like character substitutions with methods above :

sprintf(*str, "%d %s %d", 1 , word , 2);

is there something that im missing ?