How to summarise a long document with AI

Which AI to use for this

Step by step

1. 1

   Say what the summary is FOR

   "Summarise this" gets you a shorter version of everything. Say who is reading it and what they have to decide, and you get the four lines that matter to them.

   Paste thisCopy

   Summarise the document below for a landlord deciding whether to sign this contract.
   
   Rules:
   - 5 bullets maximum
   - Keep every number and date exactly as written
   - Keep any condition, exception or caveat, even a small one
   - If something is unclear in the original, say so rather than smoothing it over
   - Don't add anything that isn't in the document
   
   DOCUMENT:
   [paste the text here]

   Change the reader and the decision to yours. That one clause does more than any other instruction on this page.

2. 2

   Ask what it left out

   The most useful question you can ask a summary. It surfaces the paragraph you would have wanted to know about, and it takes one line.

   Paste thisCopy

   What did you leave out of that summary that someone in my position might regret not knowing?

3. 3

   Ask what it is unsure about

   Different question, different answer. This one finds the bits the document itself is vague on — which is usually exactly where the risk lives.

   Paste thisCopy

   Which parts of the document are genuinely ambiguous, as opposed to just badly written?

4. 4

   Check three facts against the original

   Pick the three that would cost you most if they were wrong — a figure, a date, a condition — and find them in the source document with your own eyes. Every time. This takes a minute and it is the whole reason a summary is safe to use.

5. 5

   For very long documents, do it in sections

   If it will not fit, or the answers start going vague, feed it a section at a time and then summarise the summaries. Quality drops long before the length limit does.

   Paste thisCopy

   This is part 2 of 4. Summarise just this part in 5 bullets, same rules as before. Don't try to conclude anything yet — I'll give you the rest.

What a good answer looks like

Not a made-up example. This is one of the summarising tasks from our published suite, and what Claude Opus 4.8 actually wrote when it sat it — printed exactly as it was stored, with the mark the judges gave it.

One thing to know before you read it: it was marked against the rules that task sets, which are not the rules on this page. A test suite has to stay identical for every model that sits it, so it cannot adopt the tighter prompt above. Read the answer for the shape of a good one — facts early, constraint respected, a clear next step — not as a template to copy.

- Q3 revenue up 12% to £1.4m, boosted by new retail channel.
- Retail channel contributed £310k to overall growth.
- Margins fell from 41% to 37% on shipping and warehouse costs.
- Headcount flat at 34; cash at bank £620k.
- Key Q4 risk: supplier contract expires November, not yet renegotiated.

The full answer, all twelve tasks and every judge’s score →

Common mistakes

• Acting on the summary without opening the document.

  Check the three facts that would cost you most. A summary is a map, and you do not sign a contract because the map looked fine.

• Asking it to summarise a link.

  Unless the AI genuinely has web access it will summarise what it remembers about that page, or invent a plausible version. Paste the text.

• Accepting a summary with no caveats in it.

  Real documents have conditions. A summary with none has almost certainly dropped one — ask the question in step 2.

• Summarising a confidential document in a free AI account.

  Read what the company does with what you type first. Several of them keep it indefinitely, and some train on it unless you turn that off.

Questions people ask