diff --git a/roles/cinder/README.md b/roles/cinder/README.md
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--- a/roles/cinder/README.md
+++ b/roles/cinder/README.md
@@ -1,5 +1,11 @@
 # `cinder`
 
+This role deploys the OpenStack Block Storage service using the vendored Cinder
+Helm chart. It configures the API, scheduler, and volume services used by the
+deployment.
+Backend-specific chart values can be supplied through the role variables.
+Those values are merged with the generated chart defaults during deployment.
+
 ## Operations
 
 ### Auditing orphan attachments