[support] CCK API to Add Field to Node Type

I am googling but not finding docs on how a module could add/remove a CCK field to/from a node type. I found this http://api.audean.com/api/file/files/contributions/docs/developer/examples/n... but this seems to do it all "manually" and not via CCK. Perhaps I am just missing it however... Anyhow, can anyone share with me how to do this? Thanks!