Customizing JSON API to return few records

just Add the following method in to the Model ...
def as_json(options = {})
    {
      name: self.name,                # Whatever you want to show
      city: self.city,
      country: self.country,
      customer_id: self.customer_id
   
         }
  end
--------------------------OR---------------------------------------
you can call the .select method in the API controller
like
class Api::V1::YoursController < ApplicationController
  def show
  @your = Your.select('one, two').find(params[:id])
  respond_to do |format|
        format.json {render :json => @your}
        format.xml {render :xml => @your}
    end
 end
end