diff --git a/services/lib/src/BaseReactor.h b/services/lib/src/BaseReactor.h
--- a/services/lib/src/BaseReactor.h
+++ b/services/lib/src/BaseReactor.h
@@ -12,10 +12,20 @@
 
 class BaseReactor {
 public:
+  // Returns a status holder that consists of:
+  // - reactor's state,
+  // - status of the operation that's being performed by this reactor.
   virtual std::shared_ptr<ReactorStatusHolder> getStatusHolder() = 0;
+  // Should be called when we plan to terminate the connection for some reason
+  // either with a success or a failure status.
+  // Receives a status indicating a result of the reactor's operation.
   virtual void terminate(const grpc::Status &status) = 0;
+  // Validates current values of the reactor's fields.
   virtual void validate() = 0;
+  // Should be called when `OnDone` is called. gRPC calls `OnDone` when there 
+  // are not going to be more rpc operations.
   virtual void doneCallback() = 0;
+  // Should be called when `terminate` is called.
   virtual void terminateCallback() = 0;
 };