How to analyse documents with ChatGPT or Claude

Decide what you need from the document

“Summarise this” often produces a neat overview without answering your actual question. Start with the decision: which supplier needs clarification, what changed between versions, or what must happen before a project can start?

OpenAI documents working with uploaded files. Anthropic documents file analysis and creation, including common business formats. Supported types, limits, document features and workplace settings vary. Check that the tool can read the material you have supplied before trusting a detailed answer.

Prepare a document you are allowed to share

Begin with a public or fictional document. For company work, use your organisation’s approved account and data rules. Keep an untouched original so you can compare the result.

Check whether the document contains scanned pages, small tables, diagrams, footnotes or tracked changes. These details can affect interpretation. If the tool cannot read a section, provide a clearer permitted extract. Do not assume a successful upload means every part was understood.

Use a two-pass method

First extract evidence; then ask for a conclusion. Separating these steps makes it easier to catch a missing qualification before it becomes a recommendation.

1. Upload the approved file and ask which documents, versions and sections are readable. Treat the answer as a starting check, not proof of complete coverage.
2. State the questions you want answered. For a supplier proposal, ask about deliverables, exclusions, timing and assumptions.
3. Request an evidence table with the answer, source location and a short supporting extract.
4. Open the original and verify the claims that could change your decision, including relevant footnotes.
5. Ask for a concise summary using only the verified facts. Keep gaps and unresolved questions visible.

Copy this document comparison prompt

Use this original prompt with two fictional supplier proposals, or documents your organisation has approved for the tool.

Compare these two proposals using only the supplied documents. Do not use web information. For each, extract deliverables, exclusions, timetable, responsibilities and assumptions. For every important claim give the filename and page or section, plus a short supporting extract. If a page number is unavailable, identify a heading and nearby text. Write “not found” when the document does not state something. Separate what the proposals say from your interpretation. Finish with the five questions we should ask before making a decision. Do not choose a winner yet.

Look for the exception that changes the answer

Imagine one proposal says “installation included” in the overview but excludes weekend installation in a later note. A summary that repeats the overview alone could lead you to compare unlike offers. Ask the tool to search for exclusions and conflicting statements, then check those passages yourself.

A missing statement is also different from a negative statement. “No maintenance fee found” does not prove maintenance is free. Keep that as a question for the supplier. The same rule applies to dates, responsibilities and service commitments.

If the material involves legal, tax or other professional advice, use the extraction to prepare questions for the relevant adviser. Do not treat an AI interpretation as their advice.

Check numbers outside the summary

For a spreadsheet or financial table, confirm the units, period and sign convention before interpreting totals. Are the figures dollars or thousands? Are they monthly or annual? Are discounts already included?

Use the source spreadsheet or a calculator to verify decision-critical arithmetic. If the AI produces a new workbook, inspect formulas and totals in that file. A correctly written explanation does not establish that the exported workbook calculates correctly.

For a document comparison, also check versions. A draft from June and a final version from September may differ because the agreement changed, rather than because one tool extracted it badly.

Save an answer someone else can audit

Keep the final summary with the source filenames, versions, date checked and unresolved questions. Another colleague should be able to follow the evidence without repeating the whole conversation.

For help practising document analysis with your team, use the workshop enquiry form on the 27 AI homepage.

Common questions

Can I upload a PDF and trust the summary?

Use the summary as a draft. Check important facts, tables, exceptions and source locations in the original. Some material may not be fully readable or correctly interpreted.

What if the AI invents a page reference?

Open the document and verify the passage. If the reference is wrong, ask for a heading and supporting extract, then locate it yourself. Remove any claim you cannot substantiate.

Should I ask the AI to search the web as well?

Only if outside information is needed. For a document-only comparison, say so explicitly. Keep document facts and external context separate.