How to summarise a long document with AI

By the end of this, you will have a clear, trustworthy summary of a long document, pitched at the length and focus you actually need.

What you will need

• Any AI chat tool: Claude, ChatGPT, or Gemini all work well.
• The document you want summarised, as text you can copy and paste.
• About ten minutes.

Step 1: Paste the document and set the scene

Open your AI tool and start by telling it what the document is and what you want. Then paste the text. Giving it that context first helps it summarise for the right purpose.

I'm going to paste a long report below. Please read it, and I'll then ask
you to summarise it. Here it is:

[paste your document]

What to expect: the AI will usually confirm it has read the document and is ready. If the document is very long, see the note on length at the end.

Step 2: Ask for the summary you actually want

A vague request gets a vague summary. Be specific about length, focus, and who the summary is for.

Summarise this in about 150 words for a colleague who has not read it.
Focus on the main recommendation and the two or three reasons behind it.
Use plain English and avoid jargon.

What to expect: a tight summary aimed at the reader and purpose you named. If it is too long, too short, or focused on the wrong thing, say so and ask again. This back-and-forth is normal and quick.

Step 3: Check it against the original

This step matters, so do not skip it. AI can occasionally introduce a detail that was not in the source, so treat the summary as a draft to verify, not gospel.

List the three main claims in your summary, and for each one, quote the
line from the original document it came from.

What to expect: the AI will point to the supporting lines. If it cannot find a source for a claim, that claim may have crept in by mistake, and you will know to cut or correct it.

Wrapping up

You now have a summary you can trust, because you have checked it rather than taken it on faith. From here you can ask the AI to turn the summary into bullet points, an email, or a set of talking points, whatever you need next. The same three-step rhythm, set the scene, ask specifically, then verify, works for almost any document.

A note on very long documents: every AI tool can only hold so much text at once, a limit called the context window. If your document is very long and the AI seems to lose track of the early parts, split it into sections, summarise each, and then ask the AI to combine those summaries into one.