Here's a breakdown:
"Set" is a good choice for:
* A group of tools designed for a specific purpose: "A set of screwdrivers", "a set of wrenches", "a set of gardening tools".
* A collection of tools that are usually kept together: "The mechanic's tool set was missing a socket wrench."
Other collective nouns for tools:
* Kit: This emphasizes a more portable and complete collection of tools: "A carpenter's tool kit", "a first-aid kit".
* Assortment: This implies a wider variety of tools: "An assortment of tools for DIY projects".
* Arsenal: This suggests a large and powerful collection, often used for a specific task: "The blacksmith's arsenal of tools".
Ultimately, the best collective noun depends on the specific tools and the context of the sentence.