This is a rather "simple" but IMHO very useful little mod for builders.
The Builder's Watering Can is basically a watering can that only works on grass-blocks (but with a twist).
The idea is to give players more control over what happens when they bonemeal an area.
Usually when you bonemeal an area you end up with tons of flowers and grass which looks kinda messy. A lot of people I know remove all/most flowers and some of the grass to make it look better.
And thats the basic idea for the watering can. If you hold it in your hand you can shift-rightclick and a GUI pops up which allows you to configure a few things:
the amount of grass: 0%, 25%, 50%, 75%, 100%
the amount of tall grass: 0%, 25%, 50%, 75%, 100%
the amount of flowers: 0%, 25%, 50%, 75%, 100%
Additionally to these settings, it also has its own inventory for bone meal (which is used up when you use the watering can).
The settings work like this:
For the "grass" and "flowers"-setting, 100% means that the watering can would work just like regular bone meal. Lower values mean a lower chance of stuff growing -> lets say for regular bone meal there is a 50% chance that grass grows on a grass block if you use it.
If you set the grass-percentage to "50%", the regular "50%"-chance is lowered to 25%.
If the percentage of tall-grass is changed, then x % of the regular grass that grows is turned into tall grass (each tall grass "costs" an additional bone meal).
Instead of just bone meal, the watering can could also use bone meal + water and store this as some kind of fertilizer. Each "action" (growing a flowser, growing grass, growing tall grass) would use a certain amount of that fertilizer. This would allow a better usage of bone meal.