2 level responses
In an Auction 1S - P - 2H , most Acol players would expect the 2H bid to mean 5 or more. Is it legal to have a partnership
understanding that it might only be 4, and would there be a need to Alert? If there was an understanding of 5+, but occasionally it was bid on 4, when does 4 become the partnership understanding?
Many thanks. RG
Comments
It is legal to agree 4 - what do you bid with various balanced hands which can't raise 1M opening? - and 4 cards is not alertable.
Any agreement is legal for responses (at EBU Level 4).
Responding 2C on 3=4=3=3 is natural, and the Blue Book used to mention this agreement did not require an alert.
What about "Tell them what you play"?
If the majority of the field will play it as showing 5, then a 4 card suit is unexcpected.
I can play weak 2s as 5+ cards and 3-6 HCP, but at my club I would expect to make my opponents aware of this.
2S as 5+ cards and 3-6 HCP is announced as "weak". This announcement can be extended.
EBU Blue Book announcements are intended to be a extended form of alerts not a complete explanation. Like alerts, announcements are intended to suggest that opponents ask about the call, to get all the detail.