diff --git a/python/damask/_result.py b/python/damask/_result.py
index 6ffbd0352..5b6ac71d5 100644
--- a/python/damask/_result.py
+++ b/python/damask/_result.py
@@ -115,8 +115,6 @@ class Result:
                 self.cells  = f['geometry'].attrs['cells']
                 self.size   = f['geometry'].attrs['size']
                 self.origin = f['geometry'].attrs['origin']
-            else:
-                self.add_curl = self.add_divergence = self.add_gradient = None                      # type: ignore
 
             r = re.compile(rf'{prefix_inc}([0-9]+)')
             self.increments = sorted([i for i in f.keys() if r.match(i)],key=util.natural_sort)
@@ -1313,8 +1311,8 @@ class Result:
 
         Notes
         -----
-        This function is only available for structured grids,
-        i.e. fields resulting from the grid solver.
+        This function is implemented only for structured grids
+        with one constituent and a single phase.
 
         """
         def curl(f: DADF5Dataset, size: np.ndarray) -> DADF5Dataset:
@@ -1342,8 +1340,8 @@ class Result:
 
         Notes
         -----
-        This function is only available for structured grids,
-        i.e. fields resulting from the grid solver.
+        This function is implemented only for structured grids
+        with one constituent and a single phase.
 
         """
         def divergence(f: DADF5Dataset, size: np.ndarray) -> DADF5Dataset:
@@ -1371,8 +1369,8 @@ class Result:
 
         Notes
         -----
-        This function is only available for structured grids,
-        i.e. fields resulting from the grid solver.
+        This function is implemented only for structured grids
+        with one constituent and a single phase.
 
         """
         def gradient(f: DADF5Dataset, size: np.ndarray) -> DADF5Dataset:
@@ -1410,13 +1408,13 @@ class Result:
             Arguments parsed to func.
 
         """
-        if len(datasets) != 1 or self.N_constituents != 1:
-            raise NotImplementedError
+        if self.N_constituents != 1 or len(datasets) != 1 or not self.structured:
+            raise NotImplementedError('not a structured grid with one constituent and a single phase')
 
         at_cell_ph,in_data_ph,at_cell_ho,in_data_ho = self._mappings()
 
         increments = self.place(list(datasets.values()),False)
-        if not increments: raise RuntimeError("received invalid dataset")
+        if not increments: raise RuntimeError('received invalid dataset')
         with h5py.File(self.fname, 'a') as f:
             for increment in increments.items():
                 for ty in increment[1].items():
@@ -1722,9 +1720,14 @@ class Result:
             Defaults to False, i.e. the XDMF file expects the
             DADF5 file at a stable relative path.
 
+        Notes
+        -----
+        This function is implemented only for structured grids with
+        one constituent and a single phase.
+
         """
         if self.N_constituents != 1 or len(self.phases) != 1 or not self.structured:
-            raise TypeError('XDMF output requires structured grid with single phase and single constituent.')
+            raise NotImplementedError('not a structured grid with one constituent and a single phase')
 
         attribute_type_map = defaultdict(lambda:'Matrix', ( ((),'Scalar'), ((3,),'Vector'), ((3,3),'Tensor')) )
 
@@ -1949,6 +1952,11 @@ class Result:
         target_dir : str or pathlib.Path, optional
             Directory to save DREAM3D files. Will be created if non-existent.
 
+        Notes
+        -----
+        This function is implemented only for structured grids with
+        one constituent.
+
         """
         def add_attribute(obj,name,data):
             """DREAM.3D requires fixed length string."""
@@ -1964,11 +1972,10 @@ class Result:
             return obj[name]
 
         if self.N_constituents != 1 or not self.structured:
-            raise TypeError('DREAM3D output requires structured grid with single constituent.')
+            raise NotImplementedError('not a structured grid with one constituent')
 
         N_digits = int(np.floor(np.log10(max(1,self.incs[-1]))))+1
 
-
         at_cell_ph,in_data_ph,_,_ = self._mappings()
 
         out_dir = Path.cwd() if target_dir is None else Path(target_dir)
diff --git a/python/damask/util.py b/python/damask/util.py
index eda668564..0688fca80 100644
--- a/python/damask/util.py
+++ b/python/damask/util.py
@@ -618,7 +618,7 @@ def _docstringer(docstring: _Union[str, _Callable],
                                           adopted_,
                                           flags=_re.MULTILINE|_re.DOTALL).group('content')
             except AttributeError:
-                raise RuntimeError(f"Function docstring passed for docstring section '{key}' is invalid:\n{docstring}")
+                raise RuntimeError(f"function docstring passed for docstring section '{key}' is invalid:\n{docstring}")
 
             docstring_indent, adopted_indent = (min([len(line)-len(line.lstrip()) for line in section.split('\n') if line.strip()])
                                                 for section in [docstring_, adopted_])
diff --git a/python/tests/test_Result.py b/python/tests/test_Result.py
index bad55c98d..d6bbd63a8 100644
--- a/python/tests/test_Result.py
+++ b/python/tests/test_Result.py
@@ -478,6 +478,10 @@ class TestResult:
                 for attr in dset.attrs:
                     assert np.array_equal(dset.attrs[attr],cur[path].attrs[attr])
 
+    def test_export_DREAM3D_invalid(self,res_path):
+        with pytest.raises(NotImplementedError):
+            Result(res_path/'4grains2x4x3_compressionY.hdf5').export_DREAM3D()
+
 
     def test_XDMF_datatypes(self,tmp_path,single_phase,update,res_path):
         for what,shape in {'scalar':(),'vector':(3,),'tensor':(3,3),'matrix':(12,)}.items():
@@ -509,7 +513,7 @@ class TestResult:
         assert dim_vti == dim_xdmf and bounds_vti == bounds_xdmf
 
     def test_XDMF_invalid(self,default):
-        with pytest.raises(TypeError):
+        with pytest.raises(NotImplementedError):
             default.export_XDMF()
 
     def test_XDMF_custom_path(self,single_phase,tmp_path):