Summarization

It's a choice, not a compression

Ask for a summary and it's easy to picture an AI compressing the text. What actually happens is a judgment call about what to keep and what to drop. Keep two paragraphs out of ten, and the other eight just got decided to matter less.

That judgment comes from what it learned during training — pairs of countless human-written pieces alongside their own headlines, conclusions, and abstracts, building a sense of "in writing like this, this is usually the part that comes first."

That's why an AI's summary tends to be reasonably sound but not necessarily what fits you. If what you actually wanted today wasn't the conclusion but the counterargument, a generic summary cuts exactly that part.

Extracting versus rewriting

Summarizing splits into two long-standing approaches. One pulls sentences straight out of the original that look important and strings them together. Nothing gets added that wasn't in the original, but the sentences can feel disconnected, and a pronoun's referent sometimes disappears.

The other reads the whole thing and writes new sentences from scratch. It can pull a story scattered across several paragraphs into one sentence, which reads far better — but wording that wasn't in the original can slip in during the rewrite.

Most summaries an AI service produces today lean toward rewriting. For writing where exact wording matters — a contract, a set of medical instructions, anything you'll need to check against the original — it's safer to ask for extraction, with the source sentences shown alongside.

You need to say who's reading

"Summarize this" by itself is like asking for meeting minutes without saying who they're going to. Tell it who's reading and what it's for, and the result changes considerably.

Length is worth setting too. Three lines or one paragraph, a list or flowing prose — how much information survives shifts with the choice. Specifying a shape, something like "split what's decided from what's still open," cuts down on things going missing.

It's fine if the first attempt isn't great. Point out "the budget part is missing" and the next summary comes back noticeably better.

A long document gets folded twice

There's a hard limit on how much text an AI can take in at once. Something as long as an entire book won't fit whole, so it gets split into a front, middle, and back section, each summarized separately, and those summaries get summarized again.

This approach makes long documents workable, but it costs something twice over. Whatever got dropped in the first pass has no chance of making it into the second. Anything that spans a long stretch — a condition set in chapter three that gets reversed in chapter nine — is especially likely to vanish.

Where a chunk gets cut off matters too. Cut in the middle of a paragraph and that paragraph's conclusion never survives intact in either piece.

Certain things go missing on cue

The things that disappear most often from a summary are numbers, deadlines, conditions, and the word "not." "The budget was approved, but spending doesn't start until Q3" shrinking down to just "budget approved" is a textbook case.

Drop a negation and the meaning can flip outright. "Not recommended" turning into "recommended" sends a reader moving in exactly the wrong direction. When a conclusion carries a condition, it's worth asking to see that original sentence alongside the summary.