Summarizing long documents is one of the most useful things AI assistants do. Contracts, research reports, policy papers, meeting transcripts and long email threads can all be condensed in seconds. The challenge is making sure the summary is faithful to the original, and that it highlights what you actually need.
Updated September 2026: we added research on how models handle very long inputs and links to the notebook and project tools mentioned.
Step 1: Give it the real document
Upload the file or paste the full text rather than asking about a document by name. Summaries of text the model can read are far more accurate than answers from memory, which are prone to hallucinations.
Most major assistants accept PDFs, Word files and spreadsheets. Scanned documents may need text recognition first; if the summary seems to ignore parts of the file, that is a common cause.
Step 2: Say what the summary is for
“Summarize this” produces a generic overview. A purpose produces a useful one. Compare:
- “Summarize this report.”
- “I am deciding whether to renew this vendor contract. Summarize the renewal terms, pricing changes, termination conditions and any obligations on our side.”
The second prompt tells the assistant what to look for and what to ignore.
Step 3: Ask for a structure
Useful formats include:
- A three-sentence executive summary followed by key points
- A table of decisions, owners and deadlines
- Pros and cons, or risks and mitigations
- A list of every number, date and deadline in the document
Step 4: Ask for page or section references
Request that each key point include the section or page it came from. This makes spot-checking fast and discourages the model from adding things that are not in the document.
Step 5: Verify the critical details
For anything you will act on, open the original and confirm the numbers, dates, names and obligations. Summaries are most likely to go wrong on exact figures, on qualifiers such as “except” and “unless”, and on material buried in appendices and footnotes.
Try this follow-up After the summary, ask: “What important details did this summary leave out, and what would a skeptical reader question?” It often surfaces caveats the first pass skipped.
Handling very long documents
Modern assistants can read very long inputs, but attention is not perfectly even across a huge document. Researchers call one version of this problem being "lost in the middle": models tend to use information at the start and end of a long input better than information in the middle. For book-length material:
- Summarize section by section, then ask for an overall summary of the section summaries.
- Ask targeted questions rather than relying on one big summary.
- Tools built for your own sources, such as Google’s Gemini Notebook (formerly NotebookLM) or project features in ChatGPT and Claude, help when you return to the same material repeatedly.
Confidentiality
Before uploading contracts, financial records or anything containing personal data, check your organization’s AI policy and the privacy settings of the tool. Business plans usually offer stronger data protections than consumer accounts.
A summary you can trust
Give the AI the full document, tell it why you need the summary, ask for references and verify what matters. That turns a quick overview into a summary you can confidently act on. For more on crafting the request, see our prompting guide.
Sources
- Lost in the Middle: How Language Models Use Long Contexts, arXiv, 2023
- NotebookLM is now Gemini Notebook, Google, July 2026
- What are projects?, Claude Help Center
