diff --git a/slapos/README.proxy.txt b/slapos/README.proxy.txt
index afab973c98db690b98914527fca371072300c937..8f1c9e1a5001627783c5832463421f5eb2e5a59c 100644
--- a/slapos/README.proxy.txt
+++ b/slapos/README.proxy.txt
@@ -1,2 +1,13 @@
 proxy
 =====
+
+Implement minimalist SlapOS Master server without any security, designed to work
+only from localhost with one SlapOS Node (a.k.a Computer).
+
+It implements (or should implement) the SLAP API, as currently implemented in
+the SlapOS Master (see slaptool.py in Master).
+
+The only behavioral difference from the SlapOS Master is:
+
+When the proxy doesn't find any free partition (and/or in case of slave
+instance, any compatible master instance), it will throw a NotFoundError (404).