diff --git a/operators/cuda/mul_sigmoid.h b/operators/cuda/mul_sigmoid.h
index 433e4e8ba..1eb8f2702 100644
--- a/operators/cuda/mul_sigmoid.h
+++ b/operators/cuda/mul_sigmoid.h
@@ -8,6 +8,9 @@
 
 namespace contrib {
 
+/**
+* MulSigmoid(X) = X * Sigmoid(X)
+*/
 template <typename T>
 struct MulSigmoid {
   template <typename TDict>
@@ -31,6 +34,9 @@ struct MulSigmoid {
   }
 };
 
+/**
+* MulSigmoid(X, Y) = X * Y * Sigmoid(Y)
+*/
 template <typename T>
 struct MulMulSigmoid {
   template <typename TDict>