Here are two examples of using json search API https://www.drupal.org/project/jsonapi_search_api
json search api also lets you search http://freida-admin.lndo.site/api/index/searchstax_jlb_index?filter[ful…
or
http://freida-admin.lndo.site/api/index/searchstax_jlb_index?filter[fie…