improve documentation for when to use a named matcher

docs/_api-mocking/mock_matcher.md

@@ -3,6 +3,9 @@ title: "matcher"
 position: 1.1
 description: |-
   Criteria for deciding which requests to mock.
+
+  Note that if you use matchers that target anything other than the url string, you may also need to add a `name` to your matcher object so that a) you can add multiple mocks on the same url that differ only in other properties (e.g. query strings or headers) b) if you [inspect](#api-inspectionfundamentals) the result of the fetch calls, retrieving the correct results will be easier. 
+  {: .warning}
 types:
   - String
   - RegExp