diff --git a/synapse/federation/send_queue.py b/synapse/federation/send_queue.py
index c26da7acf..657a93049 100644
--- a/synapse/federation/send_queue.py
+++ b/synapse/federation/send_queue.py
@@ -238,6 +238,8 @@ class FederationRemoteSendQueue(object):
         if from_token > self.pos:
             from_token = -1
 
+        # list of tuple(int, BaseFederationRow), where the first is the position
+        # of the federation stream.
         rows = []
 
         # There should be only one reader, so lets delete everything its
@@ -476,14 +478,15 @@ BufferedToSend = namedtuple("BufferedToSend", (
 
 
 def process_rows_for_federation(federation_sender, rows):
-    """Parse a list of rows from the federation stream and them send them out.
+    """Parse a list of rows from the federation stream and put them in the
+    transaction queue ready for sending to the relevant homeservers.
 
     Args:
         federation_sender (TransactionQueue)
-        rows (list(FederationStreamRow))
+        rows (list(synapse.replication.tcp.streams.FederationStreamRow))
     """
 
-    # The federation stream containis a bunch of different types of
+    # The federation stream contains a bunch of different types of
     # rows that need to be handled differently. We parse the rows, put
     # them into the appropriate collection and then send them off.
 
@@ -505,7 +508,6 @@ def process_rows_for_federation(federation_sender, rows):
         parsed_row = RowType.from_data(row.data)
         parsed_row.add_to_buffer(buff)
 
-    # We've finished collecting, send everything off
     for destination, states in buff.presence.iteritems():
         federation_sender.send_presence(destination, states)
 
diff --git a/synapse/replication/tcp/streams.py b/synapse/replication/tcp/streams.py
index 967b459e0..369d5f242 100644
--- a/synapse/replication/tcp/streams.py
+++ b/synapse/replication/tcp/streams.py
@@ -98,8 +98,8 @@ ToDeviceStreamRow = namedtuple("ToDeviceStreamRow", (
     "entity",  # str
 ))
 FederationStreamRow = namedtuple("FederationStreamRow", (
-    "type",  # str
-    "data",  # dict
+    "type",  # str, the type of data as defined in the BaseFederationRows
+    "data",  # dict, serialization of a federation.send_queue.BaseFederationRow
 ))
 TagAccountDataStreamRow = namedtuple("TagAccountDataStreamRow", (
     "user_id",  # str