elaborate on readme

Author: elichad

docs/_compatibility/README.md

@@ -1,3 +1,9 @@
 # Compatibility pages
 
-These pages exist to maintain old permalinks which could not be managed with the `jekyll-redirect-from` plugin.
+The files in this directory exist to maintain old permalinks which are not currently (June 2024) able to be redirected with the `jekyll-redirect-from` plugin. 
+
+Do not add new website content here.
+
+For specification files, see `_specification` folder.
+
+For tool files, see [`_pages/resources/tools.md`](../pages/resources/tools.md) and [`_data/tools_list.yml`](../_data/tools_list.yml).