This is a common problem faced by many API's see how twitter, Facebook and all are handling it
Googling about API pagination
will also help
I suggest you add 2 optional parameters such as limit
and offset
and use them in your query
On the api side you may specify limit = 50, and offset=0 and also set the minimum and maximum for limit using a comment such as {@min 10}{@max 100}
then client wont be able to tax your server with big queries