This version of Minor Suit Stayman (MSS) uses a bid of Two Spades s after opener bids one notrump to search for a minor suit game or the suitability of notrump.
2S requires at least game invitational values.
(a) an unbalanced minor suit hand
(b) no four card major
(c) a sngleton or void.
Opener bids
(a) 2NT -- natural and suggests controls in both majors. This does not deny a four-card minor, but suggests playing in notrump.
(b) 3 of a minor -- at least four cards in the minor and suggests playing in that suit.
(c) 3NT -- natural and promises controls in both majors
(d) 3 of a major -- shows a natural suit of a control in that suit. Opener has a four card minor, but is also interested in searching for 3NT. Responder bids 3NT with a control in the other major, bids 4C without one (to find the minor suit fit).
(e) 4 of a minor -- four cards in that suit and no wasted values in the majors (strongly interested in a miinor suit game and possibly slam if responder has a good hand.
Responder's rebids
(a) Pass -- to play (obviously)
(b) 3 of a minor -- if opener has rebid 2NT, this shows a five card minor and is non-forcing. If opener has bid 3C, 3D is forcing
(c) 3NT -- signoff
(d) 4 of a minor -- If opener has bid a minor, a raise of it is invitational. If opener has not bid a minor, or if responder bids the other minor at the four level, it is forcing.
(e) Any major suit bid -- shows shortness in that suit and is a slam try.
If opponents interfere after the 2S bid, opener may
(a) pass with nothing useful to say
(b) make the usual rebid, if possible
(c) double for penalty
The most important Bidding Conventions