Currently, only default fields in Ketryx are accessible through the REST API when retrieving item details, which can be done through the Item API. Custom fields are not exposed in the standard API responses and won’t appear in the field list when querying an item. This means that while you can programmatically access core metadata like title, version, and item type, any additional custom fields configured in Ketryx (even if visible in the UI) won't be returned through API calls. 

See API result: