How to use ajax/json with validation ?

Code:

$this->return $this->response->setJSON([ // <<<<-------- $this->return $this->response... ?? or return $this->... ??
     'success'    => true,
]);

Sorry, I changed for return $this->...

I'm using responseTrait gor json response

PHP Code:

....
use ResponseTrait;
....
...
return $this->respond([
...
...
]);