How to sort projects in the GraphQL API?

The Query object has a field projects (GraphQL API Resources | GitLab) which makes it possible to get a list of projects. That field has a sort parameter, which has type String. Unfortunately, I couldn’t figure out how to use that parameter. Do you know what kind of string can be used for sorting? Typically, such a parameter would have an enum type but that doesn’t seem to be the case here.