After some trial and error, i found the below way to get the product quantity in the product itself on webservice if you don't have combinations.
Go to file /classes/Product.php
Search around line 387 for
'quantity' => array(
'getter' => 'false',
'setter' => false
),
and change it to
'quantity' => array(
'getter' => 'getMyStockforWebService',
'setter' => false
),
Then add the following method.
public function getMyStockforWebService(){
return StockAvailable::getQuantityAvailableByProduct($this->id, 0);
}
This might help someone