It's possible to generate client code using the API Blueprint apiary.apib file.
For a walkthrough see https://apimatic.docs.apiary.io/#introduction/working-with-api-descriptions-documents
Sample:
Validate the API description by sending http post request to https://apimatic.io/api/validate
header: Authorization: your_key_from_https://apimatic.io
body: content from apiary.apib
Then for code generation send http post request to https://apimatic.io/api/codegen?name=gost&format=API%20;Blueprint&template=cs_portable_net_lib
header: Authorization: your_key_from_https://apimatic.io
body: content from apiary.apib
Result of this request is a link to a zip file with the generated code, something like https://apimatic.io/api/code-generations/5bc59db85f73f/generated-sdk.
Supported languages (template parameter): cs_portable_net_lib , java_eclipse_jre_lib , java_gradle_android_lib , objc_cocoa_touch_ios_lib , angular_javascript_lib , ruby_generic_lib , python_generic_lib  , php_generic_lib  , node_javascript_lib  , go_generic_lib
Java is free while other languages are free only for the first two weeks after creating an Apimatic account...