You do that with the @return
PHPDoc comment.
For an example, take a look at the Rate Limiting Example in the explorer for
GET authors.json/{id}
you will find Response Information listing
Author ( name: string, email: string )
It is coming from the following class set as the return type
<?php
/**
* Dummy class, used only for creating swagger spec model (json schema)
* look at the generated resources json to understand
*/
class Author
{
public $name='Name';
public $email='name@domain.com';
}