diff --git a/openapi.yaml b/openapi.yaml
index e32e9913..c800ca6c 100644
--- a/openapi.yaml
+++ b/openapi.yaml
@@ -728,10 +728,10 @@ paths:
                         description: >-
                           The currency the back-end is billing in. The currency
                           MUST be either a valid currency code as defined in
-                          ISO-4217 or a proprietary currency, e.g. tiles or
-                          back-end specific credits. If set to the default value
-                          `null`, budget and costs are not supported by the
-                          back-end and users can't be charged.
+                          ISO-4217 or a back-end specific unit that is used for
+                          billing such as credits, tiles or CPU hours.
+                          If set to the default value `null`, budget and costs are
+                          not supported by the back-end and users can't be charged.
                         type: string
                         nullable: true
                         default: null