diff --git a/include/openthread/heap.h b/include/openthread/heap.h
index 101861953..ca93be3fe 100644
--- a/include/openthread/heap.h
+++ b/include/openthread/heap.h
@@ -74,10 +74,18 @@ typedef void (*otHeapFreeFn)(void *aPointer);
 
 // This is a temporary API and would be removed after moving heap to platform.
 // TODO: Remove after moving heap to platform.
+/**
+ * @note This API is deprecated and use of it is discouraged.
+ *
+ */
 void *otHeapCAlloc(size_t aCount, size_t aSize);
 
 // This is a temporary API and would be removed after moving heap to platform.
 // TODO: Remove after moving heap to platform.
+/**
+ * @note This API is deprecated and use of it is discouraged.
+ *
+ */
 void otHeapFree(void *aPointer);
 
 /**