diff --git a/openapi.yaml b/openapi.yaml
index 8d5b3069..91d11392 100644
--- a/openapi.yaml
+++ b/openapi.yaml
@@ -2262,7 +2262,7 @@ paths:
               schema:
                 $ref: '#/components/schemas/money'
             OpenEO-Identifier:
-              description: Identifier associated with the synchronous processing request.
+              description: Optionally, an identifier associated with the synchronous processing request.
               schema:
                 type: string
                 pattern: '^[\w\-\.~]+$'