diff --git a/include/mesytec-mnode/mnode_nng_proto.h b/include/mesytec-mnode/mnode_nng_proto.h
index f563127..49021f7 100644
--- a/include/mesytec-mnode/mnode_nng_proto.h
+++ b/include/mesytec-mnode/mnode_nng_proto.h
@@ -7,8 +7,17 @@
 namespace mesytec::mnode::nng
 {
 
+// Format is: [u32 size][protobuf message]
+
+// Appends size prefix and serialied message contents to the nng msg.
+// Returns the number of bytes written.
 size_t serialize_proto_to_nng(const google::protobuf::MessageLite &message, nng_msg *msg);
+
+// Deserializes a protobuf message from an nng msg.
+// Returns the number of bytes used (size prefix + message).
 size_t deserialize_proto_from_nng(google::protobuf::MessageLite &message, nng_msg *msg);
+
+// Same as above but also trims the message.
 size_t deserialize_proto_from_nng_trim(google::protobuf::MessageLite &message, nng_msg *msg);
 
 } // namespace mesytec::mnode::nng
diff --git a/src/mnode_nng_proto.cc b/src/mnode_nng_proto.cc
index 487e92b..a8f7823 100644
--- a/src/mnode_nng_proto.cc
+++ b/src/mnode_nng_proto.cc
@@ -10,7 +10,7 @@ size_t serialize_proto_to_nng(const google::protobuf::MessageLite &message, nng_
     auto messageSize = message.ByteSizeLong();
 
     if (auto res = nng_msg_realloc(msg, nng_msg_len(msg) + sizeof(u32) + messageSize))
-        return false;
+        return 0;
 
     *reinterpret_cast<u32 *>(nng_msg_body(msg)) = messageSize;
     if (!message.SerializeToArray(reinterpret_cast<u8 *>(nng_msg_body(msg)) + sizeof(u32),