Any changes to description vs guideline recently?

The model I am using has so far quite reliable extracted supplier domains from documents. I had only a short 1-liner in the description and a more detailed instruction in the guideline. As said it was quite reliable so far. But now I realized that it does not follow this prompt to well anymore – has something changed recently?
When I put everything in description it seems to work better but not 100% sure yet. Just want to better understand where to put which instructions so I can optimize.
Thx,
Roman