Hi Bartlomiej,
unfortunately there are a few issues with this.
First of all, it seems that the correct query in this case would be [is_biggantt_available] is "true", without the .value part.
Unfortunately this syntax is not supported by UQL yet, as it requires a path to be provided after the property key (the one enclosed in brackets).
For now a workaround would be, if at all possible on your part, to put this JSON as property value, instead of just true:
{ "value": true}
If you do this, your original query should work.
Regards,
Simone