[righthand]

You may be interested in tools that parse XML, I'm sure there are libraries for parsing RSS/Atom specifically. I'm not sure what you're asking exactly. You want a tool that will read RSS feeds then reformat the data to a different (JSON?) format or something and have an API endpoint return that converted format? But then for what purpose of transforming the XML(an already suitable format)?

[suslik]

Yeah, perhaps I did not explain myself correctly (or, to be precise, explained myself incorrectly - I should not comment right after waking up). I want a tool that would take as input one or more RSS feeds and emits an aggregated RSS which I can then open in an RSS reader. I would then do certain things with the RSS entries (for instance, for some academic journals only the header of the article is emitted, so I can attach the full text or even an AI summary to it).