Slightly Odd 2NT opener
My partner and I are thinking about only opening 2NT if we have a 5 card suit (finding an alternative bid if not). It's still a natural 2NT opening, so according to 4G1 it should be announced. However, opponents have a right to know about the restriction.
To announce it and say "must contain a 5 card suit" is making up our own announcing rules. To announce and alert goes against 4H3a, and to just alert against 4G1.