Thanks for the fast reply,
I need to clear some logic questions went into my mind while reading your answer. Usually AbanteCart resource locations and resource names, are sometimes heavily restricted.
Therefore my fist question
1. Create new api-controller inside /public_html/extensions/your_extension_name/admin/controller/api/catalog/attributes.php
Is the .../api/catalog/attributes.php, or any part of it, restricted or just a matter of main.php registration. Exempt the controller naming convention of course, in this case "ControllerApiCatalogAttributes" I think.
3. Use some of api-controllers from core (for ex. public_html/admin/controller/api/index/login.php etc) as example
Can I put the statement to conclusion, any controller necessary to fulfill my internal process logic.