Is collective noun for tools is bag?

"Bag" is not a collective noun for tools. While you might put tools in a bag, a bag isn't a word that describes a group of tools.

Here are some collective nouns that might work for tools:

* Set: A set of tools

* Assortment: An assortment of tools

* Kit: A tool kit

* Arsenal: An arsenal of tools (implies a large or powerful collection)

* Array: An array of tools

* Collection: A collection of tools

The best choice will depend on the specific context.