diff --git a/README.md b/README.md
index 25bd5b8..0bd2a94 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ This is an open-source client library communicating with the Mujin Controller We
 
 - Versions have three numbers: MAJOR.MINOR.PATCH
   
-  - All versions with the same MAJOR.MINOR number have the same API ande are ABI compatible.
+  - All versions with the same MAJOR.MINOR number have the same API and are ABI compatible.
 
 ## Running on Linux
 
diff --git a/python/mujinwebstackclient/__init__.py b/python/mujinwebstackclient/__init__.py
index 3c0472d..8a45f00 100644
--- a/python/mujinwebstackclient/__init__.py
+++ b/python/mujinwebstackclient/__init__.py
@@ -4,6 +4,7 @@
 from .version import __version__  # noqa: F401
 
 import six
+from typing import Optional 
 
 try:
     import ujson as json  # noqa: F401
@@ -56,16 +57,16 @@ class ClientExceptionBase(Exception):
     """client base exception"""
 
     _message = None  # the error message, should be unicode
-
-    def __init__(self, message=''):
-        if message is not None and not isinstance(message, six.text_type):
+    
+    def __init__(self, message: Optional[str]='') -> None:
+        if message is not None and not isinstance(message,  six.text_type):
             message = message.decode('utf-8', 'ignore')
         self._message = message
-
-    def __str__(self):
-        return '%s: %s' % (self.__class__.__name__, self._message)
-
-    def __repr__(self):
+    
+    def __str__(self) -> str: 
+        return u'%s: %s' % (self.__class__.__name__, self._message)
+    
+    def __repr__(self) -> str:
         return '<%s(message=%r)>' % (self.__class__.__name__, self._message)
 
 
@@ -76,8 +77,8 @@ class APIServerError(ClientExceptionBase):
     _detailInfoType = None  # str, the detailed error type given errorcode
     _detailInfo = None  # dcit, the detailed info
     _inputcommand = None  # the command sent to the server
-
-    def __init__(self, message, errorcode=None, inputcommand=None, detailInfoType=None, detailInfo=None):
+    
+    def __init__(self, message: str, errorcode: Optional[int]=None, inputcommand: Optional[str]=None, detailInfoType: Optional[str]=None, detailInfo: Optional[dict]=None) -> None:
         if message is not None and not isinstance(message, six.text_type):
             message = message.decode('utf-8', 'ignore')
         self._message = message
@@ -85,8 +86,8 @@ def __init__(self, message, errorcode=None, inputcommand=None, detailInfoType=No
         self._inputcommand = inputcommand
         self._detailInfoType = detailInfoType
         self._detailInfo = detailInfo
-
-    def __str__(self):
+    
+    def __str__(self) -> str:
         if self._message is not None:
             return _('API Server Error: %s') % self._message
 
@@ -96,7 +97,7 @@ def __repr__(self):
         return '<%s(message=%r, errorcode=%r, inputcommand=%r, detailInfoType=%r, detailInfo=%r)>' % (self.__class__.__name__, self._message, self._errorcode, self._inputcommand, self._detailInfoType, self._detailInfo)
 
     @property
-    def message(self):
+    def message(self) -> str:
         """The error message from server."""
         return self._message
 
@@ -106,16 +107,17 @@ def errorcode(self):
         return self._errorcode
 
     @property
-    def stacktrace(self):
+    def stacktrace(self) -> str:
+        """The stack trace for the error"""
         return ''
 
     @property
-    def inputcommand(self):
+    def inputcommand(self) -> Optional[str]:
         """The command that was sent to the server. Could be None."""
         return self._inputcommand
 
     @property
-    def detailInfoType(self):
+    def detailInfoType(self) -> Optional[str]:
         """string for the detai info type"""
         return self._detailInfoType
 
@@ -134,7 +136,8 @@ class AuthenticationError(ClientExceptionBase):
 
 
 class WebstackClientError(ClientExceptionBase):
-    _response = None  # http response that resulted in the error
+    """Exeption class for errors returned by the web stack client"""
+    _response = None # http response that resulted in the error
 
     def __init__(self, message='', response=None):
         super(WebstackClientError, self).__init__(message)
@@ -142,6 +145,7 @@ def __init__(self, message='', response=None):
 
     @property
     def response(self):
+        """The http response that resulted in the error"""
         return self._response