REST API: How to send dynamic query string from Android/iOS client to the server?

We have API that gives us the valuation of the car:We have built in form in our android app that has input fields as :- car version, car make year.

So, we have built input form as:

1. Drop down that lets users select the version of the car.
2. A free text field that lets users type year of manufacturing of the car.

Finally we give user submit button, once user clicks here, we pass data to valuation API:

/api/valuation/?versionid=23&year=2010

The API returns back valuation of that car i.e. $20000.

In future, we will improve this algorithm and we will include kilometers etc. field in the API?

HATEOS suggests that every action except first API action should be guided through server. How can we let server create such dynamic valuation API URL so that if more fields are introduced in API, Android/iOS sends back these added fields in the query string params?