ApiModel and ApiModelProperty description isn't rendered in swagger.json

[takezoe]

Suppose we have a following model:

@ApiModel(description = "A price for an offer.")
case class OfferPrice(
  @ApiModelProperty(description = "The amount.") amount: Double,
  @ApiModelProperty(description = "The tax amount.") taxAmount: Double,
  @ApiModelProperty(description = "The tax rate.") taxRate: Option[Double]
)

Scalatra's Swagger 2.0 support renders it as follows. descriptions are not rendered:

{
  "OfferPrice": {
    "properties": {
      "amount": {
        "type": "number",
        "format": "double"
      },
      "taxAmount": {
        "type": "number",
        "format": "double"
      },
      "taxRate": {
        "type": "number",
        "format": "double"
      }
    }
  }
}