diff --git a/cas_wrapper.py b/cas_wrapper.py
index 5f95ae4..301e07e 100644
--- a/cas_wrapper.py
+++ b/cas_wrapper.py
@@ -113,19 +113,22 @@ class CasWrapper:
         self,
         local_path: str,
     ) -> typing.Tuple[bool, typing.Optional[str]]:
+        """
+        Authenticates source by git path.
+        Returns authenticate result and source commit hash.
+        """
         is_authenticated = False
         commit_cas_hash = None
         self.ensure_login()
         try:
             result_json = self.authenticate(local_path, return_json=True)
             # it should return 0 for authenticated and trusted commits
-            is_authenticated = not bool(
-                result_json.get('status', 1))
-            commit_cas_hash = result_json.get('hash')
+            is_authenticated = not bool(result_json['status'])
+            commit_cas_hash = result_json['hash']
         # we can fall with ProcessExecutionError,
         # because source can be not notarized
         except ProcessExecutionError:
-            self._logger.exception('Cannot authenticate %s:', local_path)
+            self._logger.exception('Cannot authenticate: %s', local_path)
         return is_authenticated, commit_cas_hash
 
     def authenticate_artifact(
@@ -134,6 +137,10 @@ class CasWrapper:
         use_hash: bool = False,
         return_json: bool = False,
     ) -> bool:
+        """
+        Authenticates artifact by artifact path or hash if `use_hash` is True.
+        Returns authenticate result.
+        """
         is_authenticated = False
         self.ensure_login()
         try:
@@ -145,7 +152,7 @@ class CasWrapper:
         # we can fall with ProcessExecutionError,
         # because source can be not notarized
         except ProcessExecutionError:
-            self._logger.exception('Cannot authenticate %s:', local_path)
+            self._logger.exception('Cannot authenticate: %s', local_path)
         return is_authenticated
 
     def notarize_artifacts(
@@ -153,6 +160,11 @@ class CasWrapper:
         artifact_paths: typing.List[str],
         metadata: typing.Dict[str, typing.Any],
     ) -> typing.Tuple[bool, typing.Dict[str, str]]:
+        """
+        Notarize artifacts by their paths.
+        Returns `True` if all artifacts was succesful notarizated
+        and dict with CAS hashes.
+        """
         all_artifacts_is_notarized = True
         notarized_artifacts = {}
         self.ensure_login()
@@ -166,7 +178,8 @@ class CasWrapper:
                 try:
                     cas_artifact_hash = future.result()
                 except Exception:
-                    self._logger.exception('Cannot notarize artifact:')
+                    self._logger.exception('Cannot notarize artifact: %s',
+                                           artifact_path)
                     all_artifacts_is_notarized = False
                     continue
                 notarized_artifacts[artifact_path] = cas_artifact_hash