In KEMI scripting, the integer return code of module functions have to be compared with `<0` (the equivalent of `false` in native kamailio.cfg) or `>0` (the equivalent of `true` in native kamailio.cfg):
- https://www.kamailio.org/docs/tutorials/devel/kamailio-kemi-framework/kemi/#...
If you need more details, the right place for discussion is on sr-users mailing list.