How can I filter an index view using REST?
The solution is to add a search filter to the view.

In the view settings, under Filter Criteria, you'll see Content: Published (= Yes) and Content: Content type (= Regions) (or whatever your view is for). 


Click add. In that box that shows all the fields you can add, type Search: Search Keywords.
Tick Expose this filter to visitors, to allow them to change it.
(optional) Rename the Filter Identifier from keys to query or terms or whatever you see fit.
Save the view.


You'll then be able to make a GET http://example.com/api/regions/?_format=json&amp;keys=my+search+string!