All controls which work with Models (validation/grid etc) should recognize displayName instead of field name to allow localization.

Model.define({
     fields: {
              Description: { type: "string", displayName: "Beschreibung", validation: { required: true, maxlength: 200 } },
              Number: { type: "number", validation: { min: 0, max: 300 } }
     }
   });