diff --git a/collectd_ceilometer/common/sender.py b/collectd_ceilometer/common/sender.py
index 6b8a399..ea760b9 100644
--- a/collectd_ceilometer/common/sender.py
+++ b/collectd_ceilometer/common/sender.py
@@ -62,10 +62,24 @@ class Sender(object):
         self._failed_auth = False
 
     def _on_authenticated(self):
+        """Defines an action to be taken after auth_token acquired.
+
+        It's not defined in common sender so it should be overwritten in
+        the subclasses. It typically should set the _url_base.
+        """
         pass
 
     def _authenticate(self):
-        """Authenticate and renew the authentication token"""
+        """Authenticate and renew the authentication token
+
+        * Check if auth_token is available, if yes: return it.
+            Else: Re-check the auth_token as another thread could set it.
+        * Log a message to declare request authentication in progress.
+        * Create a keystone client if it doen't already exist.
+        * Get and store the auth_token as self._auth_token.
+        * Log errors if the authentication of the token fails.
+        return: self._auth_token
+        """
 
         # if auth_token is available, just return it
         if self._auth_token is not None:
@@ -119,16 +133,40 @@ class Sender(object):
         return self._auth_token
 
     def _create_request_url(self, metername, *args, **kwargs):
+        """Defines an action to be taken to create the request URL.
+
+        It's not defined in common sender so it should be overwritten
+        in the subclasses.
+        It typically should create the request url for the standard action
+        i.e. create/update alarm/measures.
+        """
         return None
 
     def _handle_http_error(self, exc, metername, payload, auth_token):
+        """Defines an action to handle the http error
+
+        It's not defined in common sender so it should be overwritten
+        in the subclasses.
+        It should handle any HTTP errors that are expected during operation
+        and are raised from a 4* or 5* response e.g. a resource cannot be found.
+        """
         raise exc
 
     def send(self, metername, payload, retry=0, **kwargs):
         """Send the payload to Gnocchi/Aodh
 
+        * Set-up the request by making sure there's an auth token and valid
+        endpoint.
+        * Create request URL, and raise error if it's creation fails.
+        * Try self._perform_request, and if it fails with auth error, reset
+        the auth token.
+        * Renew auth_token and try to repost, if it fails: forward error to
+        self._handle_http_error.
+
         :param retry: The number of times to attempt sending when the request
             times out. Default is 0, which does not retry.
+
+        returns:
         """
 
         # get the auth_token
@@ -190,7 +228,15 @@ class Sender(object):
 
     @classmethod
     def _perform_request(cls, url, payload, auth_token, req_type="post"):
-        """Perform the POST/PUT request."""
+        """Perform the POST/PUT request.
+
+        * Create request headers consisting of auth_token and content type.
+        * Perform request with the given payload and return its result.
+        * Raise exception if there was an error when performing request.
+        * Log the result of the request to help debugging.
+        return: response
+        """
+
         LOGGER.debug('Performing request to %s, payload=%s, req_type = %s' %
                      (url, payload, req_type))