adding note about format=API

v1.1/schema.md

@@ -504,7 +504,7 @@ Dataset Fields {#Dataset}
 **Cardinality** | (0,1)
 **Required** | No
 **Accepted Values** | String
-**Usage Notes** | This should be a human-readable description of the file format of the dataset, that provides useful information that might not be apparent from `mediaType`.  
+**Usage Notes** | This should be a human-readable description of the file format of the dataset, that provides useful information that might not be apparent from `mediaType`.  Note that `API` should always be used to distinguish web APIs.  
 **Example** | `{"format":"CSV"}`
 
 {: .table .table-striped .child-field #distribution-mediaType}