Documentation for built-in extensions

I’ve been trying out some extensions lately. The downloadable extensions on the Inform 7 website have documentation on the website, but if similar documentation exists for built-in extensions (such as Basic Screen Effects by Emily Short), I can’t find it. Is there documentation available for built-in extensions and, if there is, where can I find it?

The documentation for installed extensions (including the built-ins) can be viewed in the application: go to the Documentation tab, to the main contents page; scroll to the bottom and click Installed Extensions; then select the extension you want to view.