protected virtual Task<bool> OnSketchCompleteAsync( 
   Geometry geometry
)

//In your config.daml...set the categoryRefID
//<tool id="..." categoryRefID="esri_editing_construction_annotation" caption="Create Anno" ...>

//Sketch type Point or Line or BezierLine in the constructor...
//internal class AnnoConstructionTool : MapTool  {
//  public AnnoConstructionTool()  {
//    IsSketchTool = true;
//    UseSnapping = true;
//    SketchType = SketchGeometryType.Point;
//

protected async override Task<bool> OnSketchCompleteAsync(Geometry geometry)
{
  if (CurrentTemplate == null || geometry == null)
    return false;

  // Create an edit operation
  var createOperation = new EditOperation();
  createOperation.Name = string.Format("Create {0}", CurrentTemplate.Layer.Name);
  createOperation.SelectNewFeatures = true;

  var insp = CurrentTemplate.Inspector;
  var result = await QueuedTask.Run(() =>
  {
    // get the annotation properties class
    AnnotationProperties annoProperties = insp.GetAnnotationProperties();
    // set custom annotation properties
    annoProperties.TextString = "my custom text";
    annoProperties.Color = ColorFactory.Instance.RedRGB;
    annoProperties.FontSize = 24;
    annoProperties.FontName = "Arial";
    annoProperties.HorizontalAlignment = ArcGIS.Core.CIM.HorizontalAlignment.Right;
    annoProperties.Shape = geometry;
    // assign annotation properties back to the inspector
    insp.SetAnnotationProperties(annoProperties);

    // Queue feature creation
    createOperation.Create(CurrentTemplate.Layer, insp);

    if (!createOperation.IsEmpty)
    {
      // Execute the operation
      return createOperation.Execute(); //Execute and ExecuteAsync will return true if the operation was successful and false if not
    }
    else
      return false;
  });
  return result;
}

//Map Tool is used to perform Spatial selection.
//Graphic selection uses the selection geometry 
//to intersect the geometries of those elements (graphic or group) 
//that will be selected and then highlights them. 
protected override async Task<bool> OnSketchCompleteAsync(Geometry geometry)
{
  var selPoly = geometry as Polygon;
  return await QueuedTask.Run(() =>
  {     
    //note: the selected elements may belong to more than one layer...
    var elems = MapView.Active.SelectElements(selPoly, SelectionCombinationMethod.New);
    return true;
  });
}