If using Google Site Search (GSS) you can specify labels for different sites, so users can later refine their search with facets generated from these labels. This works fine if you can label pages according to different domains or distinct URL patterns (e.g. path segments that clearly mark different areas of your website).
However, is there a way you can make Google Site Search extract the labels from an individual page itself, for example by providing some kind of meta information or structured content in the HTML source?
context.xml
file for the CSE being used on a given page or ..?