The mechanics of calling for kan requires some assessment, as risks are involved. In plenty of cases, a kan is a risky move, even though there are potential benefits.
Under most circumstances, the call for kan is an offensive move. The player gets an extra draw from the rinshanpai and chances for the kandora. If the hand is tenpai, then the hand has a chance for rinshan kaihou.
Aiding a player
A safe place for dangerous tiles is in one's own hand. A call for ankan ensures for all four of a single tile type to remain in the hand. Furthermore, it may be possible to apply kabe making appropriate tiles look safer. For the other kan types, the hand is already open. In the case for daiminkan, the hand is either already open or about to be opened. If the tile to be called is already a safe tile, then it may be a better idea to not call, as three safe tiles are already in possession. For shouminkan or kakan, the added risk of chankan is applied.
An interesting consideration is to decline kan. This may be possible in one of two ways: Discarding the fourth tile, or simply holding on to it. Doing so prevents additional dora indicators, which could be favorable to opponents. The tile itself may be dangerous. If the hand is undergoing betaori, then there is no interest for kan in the first place.
A player may have a hand warranting for kan. Given that the play is discretionary, it may not be necessary to call kan immediately. Though, the delay of the call may actually affect tile efficiency if the extra tile is not connected to another tile in the hand.
Extra dora indicators are shown due to calls for kan. This is the kandora. While a player may chance to receive extra dora, an equal chance applies to grant other players the extra dora. With that said, extra consideration must be taken when given the opportunity to call kan.
Shifting the haiteipai