I've found Kagi's Universal Summarizer useful for:

  - Long reads when I just want to know the conclusion
  - Reading terms of services that I would otherwise have blindly accepted
  - Summarizing key requirements in large tender documents prior to bidding on work

As for summaries in general, FastGPT is so useful I apply it to most of my searches.

Especially if I'm looking for a small fact buried in the first results.