diff --git a/README.MD b/README.MD
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--- a/README.MD
+++ b/README.MD
@@ -1,5 +1,11 @@
 # HLS Arbitrary Precision Types Library
 
+This repo provides simulation code of HLS Arbitrary Precision Types.
+The code is based from headers shipped with Vivado,
+but due to absence of synthesis support **it should not be used in an HLS project targeting FPGA**.
+
+----
+
 Copyright 2011-2019 Xilinx, Inc.
 
 Licensed under the Apache License, Version 2.0 (the "License");