Filter on array length in Azure Cognitive Search

How can I fetch index records by filtering on array length?

For ex. I have an array property "Contracts". I want to fetch records where Contracts is a blank array.

All I could find in documentation is "any" (Contracts/any) and "all" (Contracts/all) but I want to use something like $filter=Contracts/count eq 0. Is there a way to filter on length of array?