Add link to the README in the main plugin's README

src/plugins/usage_collection/README.md

@@ -325,3 +325,8 @@ By storing these metrics and their counts as key-value pairs, we can add more me
 to worry about exceeding the 1000-field soft limit in Elasticsearch.
 
 The only caveat is that it makes it harder to consume in Kibana when analysing each entry in the array separately. In the telemetry team we are working to find a solution to this.
+
+# Routes registered by this plugin
+
+- `/api/ui_metric/report`: Used by UI Metrics to report the metrics to the server
+- `/api/stats`: Get the metrics and usage ([details](./server/routes/stats/README.md))