Akka Http Parameter Validation

Question

I have several get routes for my akka-http service; they all have the form:

pathPrefix("compass") {
  path("route") {
    parameters(('srclat.as[Double], 'srclon.as[Double], 
      'destlat.as[Double], 'destlon.as[Double])) {
        (srclat, srclon, destlat, destlon) =>
          complete(getRoute((LatLong(srclat, srclon), LatLong(destlat, 
            destlon))))
      }
    }
  }

Using Cats Validated data type, I am able to validate both the latitudes and longitudes passed to the method, collecting any values that exceed their ranges in a List[String]. I know there's a validate directive, but I'm not sure if it works for applicative (accumulative) style validation (so if multiple parameters are wrong, I'll get a list of all errors), but I'm not sure how to use the validate directive for this, or if there's a preferred way.

Also, I know parameters is a directive and should be able to be reused-- I have 3 get methods with the same parameters (requiring the same validation), so if there's a way to accomplish this with the least amount of boilerplate, that would be great. Thanks for any suggestions!