Structure.Testy API description is available here: http://almworks.com/testy/apidocs/v3/

We also introduced the Swagger UI, it is available via link like <You JIRA address>/rest/testy/3/rest-browser/. Our public demo JIRA instance is available at  https://demo-structure.almworks.com, so the URL for Swagger UI is https://demo-structure.almworks.com/rest/testy/3/rest-browser/ (you should be logged in JIRA first)