What survives the summary and what gets cut?
Decisions, deadlines, names, numbers and anything that asks something of you survive. Pleasantries, restated context and hedging get cut. TextAI is deliberately conservative with specifics: if a date appears in the original, it appears in the summary.
How long can the input be?
Long enough for a full email thread, a meeting transcript or a news article. For anything genuinely book-length, summarise it in sections and then summarise those summaries, you retain far more detail that way than forcing everything through in one pass.
Summarize or Key Takeaways?
TextAI has both. Summarize returns compressed prose that reads like the original. Key Takeaways returns a bulleted list of the points that matter. Use Summarize when you need to understand something and Key Takeaways when you need to act on it.
Where people use it most
Group chats after a day away from the phone. Forwarded email chains where the actual question is buried in the fourth message. Terms and conditions. Articles a friend sent that you would otherwise never open.