Streaming with Dave today, the perfect example came up of considering your shapes and waits before calling.
Nice hand, right! Half-flush, East, Dora. Does he call here?
First, let’s consider what it is worth closed and open.
Closed half-flush (2), East (1), dora (1) = 5 han
Open half-flush (3), East (1), dora (1) = 4 han
So both are mangan. However, keeping it closed means that you will have a chance to riichi for a haneman.
Because you can call into tempai relatively fast with a mangan, I would recommend calling but not on every option.
9p - Drop the haku for tempai. This will give you a 6p, 7p wait and you can upgrade that if you draw the 4p (that would give you a 1,3,4,6 wait).
8p - Drop the 9p or haku for tempai. This would leave you on a single tile wait which is less than ideal. It does give you the chance to upgrade but you may not get lucky.
6p - This is Dave’s choice here; calling 567 and dropping the haku for a 9p, 5p wait. Again, this is not a great wait as there are no 5p left (note there is a kabe) and only two 9p left. But the 9p are at the edge of the suit so more likely to be thrown. It would also be possible to upgrade if a 4p or 6p are drawn.
This formatting got a little messy but…
9p>6p>8p
9p is a no brainer, call it! It’s good! 6p, check your surroundings and if you decide to push, this is good. 8p, you really want to be sure this is the right move given the context on the table. With the context in the screencap, no. But perhaps in orasu or another situation, it would be worth it.
Dave’s USPML stream available here.
Edit 20190617: Corrections thanks to ApplySci! There are no 5p left.