Merge pull request #517 from MHBauer/get-no-creds

 GET MAY return creds unable to be used

spec.md

@@ -1188,6 +1188,13 @@ declare them as such using `"bindable": true` in the
 [Catalog](#catalog-management). Service Brokers that do not offer any bindable
 services do not need to implement the endpoint for bind requests.
 
+Service Brokers MAY choose to only return the information that represents a
+Service Binding once, either when the Service Binding is being created
+synchronously, or when the Service Binding is first fetched via the [Fetching a
+Service Binding](#fetching-a-service-binding) endpoint. However, in order for
+the Platform to successfully use the Service Binding, the information MUST be
+returned at least once.
+
 ### Types of Binding
 
 #### Credentials