When you create an attributes set, it's important that you populate it correctly since it describes almost all of the important information about your item for Spotlight. You can set a title, content description, a thumbnail image, keywords, even ratings or phone numbers, GPS information, and much, much more. For a full overview of what's possible, refer to the CSSearchableItemAttributeSet documentation. Every time you are about to create a new item that can be indexed, you should take a look at the documentation to make sure you don't miss any attributes.
The better use you make of the available attributes, the more effectively your content can be indexed and the higher your app will ...