public sealed class AnnotationProperties 

// get an anno layer
AnnotationLayer annoLayer = MapView.Active.Map.GetLayersAsFlattenedList().OfType<AnnotationLayer>().FirstOrDefault();
if (annoLayer == null)
  return;

QueuedTask.Run(() =>
{
  Inspector insp = null;
  // get the anno feature class
  var fc = annoLayer.GetFeatureClass() as ArcGIS.Core.Data.Mapping.AnnotationFeatureClass;

  // get the featureclass CIM definition which contains the labels, symbols
  var cimDefinition = fc.GetDefinition() as ArcGIS.Core.Data.Mapping.AnnotationFeatureClassDefinition;
  var labels = cimDefinition.GetLabelClassCollection();
  var symbols = cimDefinition.GetSymbolCollection();

  // make sure there are labels, symbols
  if ((labels.Count == 0) || (symbols.Count == 0))
    return;

  // find the label class required
  //   typically you would use a subtype name or some other characteristic
  // in this case lets just use the first one

  var label = labels[0];

  // each label has a textSymbol
  // the symbolName *should* be the symbolID to be used
  var symbolName = label.TextSymbol.SymbolName;
  int symbolID = -1;
  if (!int.TryParse(symbolName, out symbolID))
  {
    // int.TryParse fails - attempt to find the symbolName in the symbol collection
    foreach (var symbol in symbols)
    {
      if (symbol.Name == symbolName)
      {
        symbolID = symbol.ID;
        break;
      }
    }
  }
  // no symbol?
  if (symbolID == -1)
    return;

  // load the schema
  insp = new Inspector();
  insp.LoadSchema(annoLayer);

  // ok to assign these fields using the inspector[fieldName] methodology
  //   these fields are guaranteed to exist in the annotation schema
  insp["AnnotationClassID"] = label.ID;
  insp["SymbolID"] = symbolID;

  // set up some additional annotation properties
  AnnotationProperties annoProperties = insp.GetAnnotationProperties();
  annoProperties.FontSize = 36;
  annoProperties.TextString = "My Annotation feature";
  annoProperties.VerticalAlignment = VerticalAlignment.Top;
  annoProperties.HorizontalAlignment = HorizontalAlignment.Justify;

  insp.SetAnnotationProperties(annoProperties);

  var tags = new[] { "Annotation", "tag1", "tag2" };

  // use daml-id rather than guid
  string defaultTool = "esri_editing_SketchStraightAnnoTool";

  // tool filter is the tools to filter OUT
  var toolFilter = new[] { "esri_editing_SketchCurvedAnnoTool" };

  // create a new template 
  var newTemplate = annoLayer.CreateTemplate("new anno template", "description", insp, defaultTool, tags, toolFilter);
});

//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;
}