Checking of incoming JSON values / problems with JSON booleans

I try to check for `true` or `false` from incoming data. This value should be not empty but withh boolean checking i get an error if the value is `false`. If i try to check for anyOf it get's not recognized based on UPPERCASing the rule automatically to `TRUE` or `FALSE`.

What can i do to check the boolean fields?

Regards André
