diff --git a/dlup/annotations.py b/dlup/annotations.py
index 4ebabf11..847df580 100644
--- a/dlup/annotations.py
+++ b/dlup/annotations.py
@@ -976,12 +976,14 @@ def __add__(self, other: WsiAnnotations | Point | Polygon | list[Point | Polygon
 
         if isinstance(other, list):
             if not all(isinstance(item, (Point, Polygon)) for item in other):
-                raise TypeError("")
+                raise TypeError("can only add list purely containing Point and Polygon objects to WsiAnnotations")
             new_layers = self._layers + other
             new_tags = self.tags
         elif isinstance(other, WsiAnnotations):
             if self.sorting != other.sorting or self.offset_to_slide_bounds != other.offset_to_slide_bounds:
-                raise ValueError("")
+                raise ValueError(
+                    "Both sorting and offset_to_slide_bounds must be the same to add WsiAnnotations together."
+                )
             new_layers = self._layers + other._layers
             new_tags = self.tags if self.tags is not None else [] + other.tags if other.tags is not None else None
         else:
@@ -996,14 +998,16 @@ def __iadd__(self, other: WsiAnnotations | Point | Polygon | list[Point | Polygo
 
         if isinstance(other, list):
             if not all(isinstance(item, (Point, Polygon)) for item in other):
-                raise TypeError("")
+                raise TypeError("can only add list purely containing Point and Polygon objects to WsiAnnotations")
 
             self._layers += other
             for item in other:
                 self._available_classes.add(item.annotation_class)
         elif isinstance(other, WsiAnnotations):
             if self.sorting != other.sorting or self.offset_to_slide_bounds != other.offset_to_slide_bounds:
-                raise ValueError("")
+                raise ValueError(
+                    "Both sorting and offset_to_slide_bounds must be the same to add WsiAnnotations together."
+                )
             self._layers += other._layers
 
             if self._tags is None:
@@ -1019,10 +1023,17 @@ def __iadd__(self, other: WsiAnnotations | Point | Polygon | list[Point | Polygo
         self._str_tree = STRtree(self._layers)
         return self
 
-    def __radd__(self, other: WsiAnnotations | Point | Polygon) -> WsiAnnotations:
+    def __radd__(self, other: WsiAnnotations | Point | Polygon | list[Point | Polygon]) -> WsiAnnotations:
         # in-place addition (+=) of Point and Polygon will raise a TypeError
-        if not isinstance(other, (WsiAnnotations, Point, Polygon)):
+        if not isinstance(other, (WsiAnnotations, Point, Polygon, list)):
             return NotImplemented
+        if isinstance(other, list):
+            if not all(isinstance(item, (Point, Polygon)) for item in other):
+                raise TypeError("can only add list purely containing Point and Polygon objects to WsiAnnotations")
+            raise TypeError(
+                "use the __add__ or __iadd__ operator instead of __radd__ when working with lists to avoid \
+                            unexpected behavior."
+            )
         return self + other
 
     def __sub__(self, other: WsiAnnotations | Point | Polygon) -> WsiAnnotations:
diff --git a/tests/test_annotations.py b/tests/test_annotations.py
index b857c24e..4e055afe 100644
--- a/tests/test_annotations.py
+++ b/tests/test_annotations.py
@@ -53,6 +53,14 @@ class TestAnnotations:
     _v7_annotations = None
     _v7_raster_annotations = None
 
+    additinoaL_point_a_cls = AnnotationClass(label="example", annotation_type=AnnotationType.POINT, color=(255, 0, 0))
+    additional_point = Point((1, 2), a_cls=additinoaL_point_a_cls)
+
+    additional_polygon_a_cls = AnnotationClass(
+        label="example", annotation_type=AnnotationType.POLYGON, color=(255, 0, 0), z_index=1
+    )
+    additional_polygon = Polygon([(0, 0), (4, 0), (4, 4), (0, 4)], a_cls=additional_polygon_a_cls)
+
     @property
     def v7_annotations(self):
         if self._v7_annotations is None:
@@ -229,3 +237,111 @@ def test_annotation_filter(self):
 
         annotations.filter(["non-existing"])
         assert len(annotations._layers) == 0
+
+    def test_length(self):
+        annotations = self.geojson_annotations
+        assert len(annotations._layers) == len(annotations)
+
+    def test_dunder_add_methods_with_point(self):
+        annotations = self.geojson_annotations.copy()
+        initial_annotations_id = id(annotations)
+        initial_length = len(annotations)
+
+        # __add__
+        new_annotations = annotations + self.additional_point
+        assert initial_annotations_id != id(new_annotations)
+        assert initial_length + 1 == len(new_annotations)
+        assert self.additional_point in new_annotations
+
+        # __radd__
+        new_annotations = self.additional_point + annotations
+        assert initial_annotations_id != id(new_annotations)
+        assert initial_length + 1 == len(new_annotations)
+        assert self.additional_point in new_annotations
+        with pytest.raises(TypeError):
+            self.additional_point += annotations
+
+        # __iadd__
+        annotations += self.additional_point
+        assert initial_annotations_id == id(annotations)
+        assert initial_length + 1 == len(annotations)
+        assert self.additional_point in annotations
+
+    def test_add_with_polygon(self):
+        annotations = self.geojson_annotations.copy()
+        initial_annotations_id = id(annotations)
+        initial_length = len(annotations)
+
+        # __add__
+        new_annotations = annotations + self.additional_polygon
+        assert initial_annotations_id != id(new_annotations)
+        assert initial_length + 1 == len(new_annotations)
+        assert self.additional_polygon in new_annotations
+
+        # __radd__
+        new_annotations = self.additional_polygon + annotations
+        assert initial_annotations_id != id(new_annotations)
+        assert initial_length + 1 == len(new_annotations)
+        assert self.additional_polygon in new_annotations
+        with pytest.raises(TypeError):
+            self.additional_polygon += annotations
+
+        # __iadd__
+        annotations += self.additional_polygon
+        assert initial_annotations_id == id(annotations)
+        assert initial_length + 1 == len(annotations)
+        assert self.additional_polygon in annotations
+
+    def test_add_with_list(self):
+        annotations = self.geojson_annotations.copy()
+        initial_annotations_id = id(annotations)
+        initial_length = len(annotations)
+
+        # __add__
+        new_annotations = annotations + [self.additional_point, self.additional_polygon]
+        assert initial_annotations_id != id(new_annotations)
+        assert initial_length + 2 == len(new_annotations)
+        assert self.additional_polygon in new_annotations
+        assert self.additional_point in new_annotations
+
+        # __radd__
+        _annotations_list = [self.additional_point, self.additional_polygon]
+        with pytest.raises(TypeError):
+            new_annotations = _annotations_list + annotations
+
+        _annotations_list = [self.additional_point, self.additional_polygon]
+        with pytest.raises(TypeError):
+            _annotations_list += annotations
+
+        # __iadd__
+        annotations += [self.additional_point, self.additional_polygon]
+        assert initial_annotations_id == id(annotations)
+        assert initial_length + 2 == len(annotations)
+        assert all(ann in new_annotations for ann in annotations)
+
+    def test_add_with_wsi_annotations(self):
+        annotations = self.geojson_annotations.copy()
+        other_annotations = self.geojson_annotations.copy()
+        initial_annotations_id = id(annotations)
+        initial_length = len(annotations)
+
+        # __add__
+        new_annotations = annotations + other_annotations
+        assert initial_annotations_id != id(new_annotations)
+        assert len(annotations) + len(other_annotations) == len(new_annotations)
+        assert all(ann in new_annotations for ann in annotations)
+
+        # __iadd__
+        annotations += other_annotations
+        assert initial_annotations_id == id(annotations)
+        assert initial_length + len(other_annotations) == len(annotations)
+        assert all(ann in annotations for ann in other_annotations)
+
+    def test_add_with_invalid_type(self):
+        annotations = self.geojson_annotations.copy()
+        with pytest.raises(TypeError):
+            _ = annotations + "invalid type"
+        with pytest.raises(TypeError):
+            annotations += "invalid type"
+        with pytest.raises(TypeError):
+            _ = "invalid type" + annotations