Very Easy: For beginners. Tool either requires very limited and basic inputs or default data are available.
Easy: For users with basic technical ability. Tool requires several readily-available inputs; default data may or may not be available.
Moderate: For users with moderate technical ability. Tool requires many inputs, some of which may be challenging to obtain; default data may or may not be available.
Complex: For users with advanced technical ability. Tool requires many detailed inputs that require extensive data compilation; complete default data are not available.