Variety is a lightweight tool for MongoDB that provides a schema analyzer, allowing developers to quickly learn how data is structured and identify rare keys or outliers in the collection. It can be used to find all rare keys in a given collection and help detect potential bugs or remnant code from previous schemas. The tool's output includes information on the types of values stored for each key, as well as the total occurrences and percentage containing counts. Variety is free, open source, and written in 100% JavaScript, with documentation available on its GitHub page.