can't match route with named parameters in finatra controller

Question

I am using com.twitter.finatra.http.Controller to set up endpoints in Scala and I have an endpoint like this:

get(s"${endpoint}/:id/lookup/?") {request: Request => 
 println("here")
 val id = request.params("id")
 response.ok
}

It is my understanding that it should match the link http://myservice/123/lookup and request.params("id") should return "123". But it never gets to println. However when I try http://myservice/:id/lookup (exactly like that) - it does. So it's expecting exactly ":id" in the address rather than a dynamic value. And obviously request.params("id") is not there. If I call http://myservice/:id/lookup?id=123, then request.params("id") is 123 coming from the query string parameter

What am doing wrong or misunderstanding? I am very new to Scala, so it's entirely possible that the whole thing is set up not how it is supposed to.