add description of schemas plugin to pants-plugins/README.md
@@ -7,3 +7,15 @@ This replaces the Makefile and related scripts such that they are more discovera
The plugins here add custom goals or other logic into pants.
To see available goals, do "./pants help goals" and "./pants help $goal".
+
+These StackStorm-specific plugins are probably only useful for the st2 repo.
+- `schemas`
+
+### `schemas` plugin
+
+This plugin wires up pants to make sure `contrib/schemas/*.json` gets
+regenerated whenever the source files change. Now, whenever someone runs
+the `fmt` goal (eg `./pants fmt contrib/schemas::`), the schemas will
+be regenerated if any of the files used to generate them have changed.
+Also, running the `lint` goal will fail if the schemas need to be
+regenerated.
