Custom attributes in eclypse can be used in various cases. Generally they contain information that is used to map keys back to the source system. If you are localizing assets such as images, documents or audio files then they can also be used during export process and referenced in your export file path. According to your workflow, you may designate certain attributes as required to ensure that they are present for each key. In order to require attributes, go to your project settings and provide the required attributes that should be present. An example is shown below:

Adding New Keys

After you enable Required Attributes, "creating a new key interface" will ask users to provide values for those attributes. You cannot save a new key unless you provide a value for each required attribute. You can always edit those values at a later time.

Existing Keys

Keys that have already been added to eclypse before enabling Required Attributes will automatically see "Locked" custom attribute setting in their Advanced tab.

Checking Keys With Missing Attributes

Using eclypse's built-in filters, you can examine those keys that don't have the required attributes populated.