From Brotato Wiki
Improved Tools is a unique item. Only 1 of each unique item can be equipped, and it will then no longer be offered in the Shop, and no longer drop from loot crates.
Improved Tools gives 10% Attack Speed, and increases the attack speed and/or spawning rate of all Engineering Structures by half of your Attack Speed Stat. See the Structures page for more details on structures and their default attack speed.
So if you have +100% Attack speed Stat, Improved Tools will make Turrets attack 50% faster, and Gardens spawn Consumables 50% faster.
The Improved Tools affect all structures with the exception of Wandering Bot, which doesn't attack or spawn anything. Improved tools affect structures no matter their source, so it doesn't matter if a Turret is spawned by the item Turret, the Wrench weapon, or the Pocket Factory item.
Improved Tools tend to be very powerful on Engineering builds, provided you have the attack speed to back it up. Outside of this item, Structures don't benefit from Attack speed, so you might dump the attack speed stat and let it go into the negative values.
When planning an Engineering build, it can be a good strategy to anticipate picking up this item (especially on Due to Item Tags, the Character(s) Cyborg, Engineer have a higher chance to find these items in the Shop. that are tagged for Engineering, so this item is more likely to drop). In this case, you can build Attack Speed early in order to help this item's effect later on. But be warned that Improved Tools is far from guaranteed to drop during a run.
Finally, Improved Tools can be worth it on regular weapon builds that need the attack speed and have a few structures such as a Medical Turret or a Garden. Especially if you already have a good amount of attack speed. For example on One Armed, the 200% attack speed the character starts with, means that Improved Tools will double the attack speed of all structures.
The tooltip of items like Garden shows the drop rate rounded to the nearest second. The internal value used in the game includes decimals however. This is the case for all structures.