gistfile1.scala

scala> Json.toJson((1, 2))
<console>:20: error: No Json deserializer found for type (Int, Int). Try to implement an implicit Writes or Format for this type.
              Json.toJson((1, 2))
                         ^

scala>    implicit val x = new Writes[(Int, Int)] {
     |       def writes(t: (Int, Int)): JsValue = {
     |         JsArray(Seq(JsNumber(t._1), JsNumber(t._2)))
     |       }
     |     }
x: play.api.libs.json.Writes[(Int, Int)] = $anon$1@62ea9973

scala> Json.toJson((1, 2))
res41: play.api.libs.json.JsValue = [1,2]