Do a pre-save transform (PST) on the input, but don't parse it. Returns the same wikitext, after a PST has been applied. Only valid when used with $1text.
MediaWiki:Apihelp-parse-param-onlypst
From MTG Wiki
Do a pre-save transform (PST) on the input, but don't parse it. Returns the same wikitext, after a PST has been applied. Only valid when used with $1text.