diff --git a/TOMP-API-4-PURCHASE.yaml b/TOMP-API-4-PURCHASE.yaml
index c0f3de5..e19ec40 100644
--- a/TOMP-API-4-PURCHASE.yaml
+++ b/TOMP-API-4-PURCHASE.yaml
@@ -282,14 +282,15 @@ components:
             properties:
               inputs:
                 type: object
-                required:
-                - assets
                 properties:
                   customer:
                     $ref: "TOMP-API-1-CORE.yaml#/components/schemas/customer"
+                  stationId:
+                    type: string
+                    description: unique identifier of a station
+                    example: XX:Y:12345678
                   assets:
                     type: array
-                    minItems: 1
                     items:
                       $ref: "TOMP-API-1-CORE.yaml#/components/schemas/assetReference"
                   distribution: