diff --git a/doc/osdpctl/index.rst b/doc/osdpctl/index.rst
index 0330a1e..4a44177 100644
--- a/doc/osdpctl/index.rst
+++ b/doc/osdpctl/index.rst
@@ -1,6 +1,10 @@
 osdpctl - Tool
 ==============
 
+.. warning::
+   This tool has been deprecated. The future plan is to rewrite it in Rust, but
+   there is no ETA for it.
+
 .. toctree::
    :maxdepth: 2