diff --git a/README.rst b/README.rst
index 7a6fdac..76a9215 100644
--- a/README.rst
+++ b/README.rst
@@ -9,6 +9,10 @@ for Intel RackScale Design enabled hardware. Capabilities include logical
 node composition and decomposition, remote storage discovery and composition,
 and NVMe over PCIe drive attaching and detaching to logical nodes.
 
+It supports the API interface of RSD version 2.1, 2.2 and 2.3 now. Part of RSD
+2.4 API have been supported, and the rest of them are still under
+implementation.
+
 * Free software: Apache license
 * Documentation: https://github.com/openstack/rsd-lib/blob/master/doc/source/reference/usage.rst
 * Source: http://git.openstack.org/cgit/openstack/rsd-lib