How Do You Check a Claude Summary Against the Source?
Have Claude tie each claim to a word-for-word quote, then look up the claims you'll rely on in the original. A summary can read perfectly and still drop a qualifier or shift a number, so check the figures, quotes and conclusions that matter.
<document> [paste the source] </document> Summarize this for [reader] in [length]. Then add a table with one row for each claim, figure or quote in your summary. Columns: claim, exact supporting quote, location (section or page). If you can't find an exact quote for a claim, remove it from the summary and mark where it was with []. Label anything you inferred as "inferred." If the document doesn't address something, say so.
- 1Pull exact quotes
- 2Write from the quotes
- 3Match each claim to a quote
- 4Remove what has no quote
Try it now
- 1Attach or paste a document you need to rely on, and send the prompt above.
- 2Pick the three claims you'd act on. Use your document viewer's find command to search for each quote.
- 3Read the sentences around each quote. You'll know the check worked when you've confirmed each one exists and still means the same thing in context.
Use it when
When a summary feeds something that matters: a figure in a board deck, a quote you'll publish, a contract term you'll rely on, or a study you'll cite. It matters most for long sources you haven't read.
Skip it when
When you only want the gist of a casual article, and being approximately right costs nothing. Skip the quote step for short documents too, where reading the original is about as quick.
Why it works
Anthropic's hallucination guide suggests two steps that make this practical. For documents over 20,000 tokens, ask Claude to extract exact quotes before doing the task. Then have it find a supporting quote for each claim and remove any claim without one. Anthropic says these techniques significantly reduce hallucinations, but don't eliminate them, and it says to validate critical information. Quotes make your check faster because you can search for them. On the API, the Citations feature goes further: the docs say citations are guaranteed to contain valid pointers to the documents you provided, and cited_text doesn't count toward output tokens. A valid pointer shows where a passage is, but you still have to judge whether it supports the claim.
Example
Say a summary reads "the policy cut costs by 30%." The table's supporting quote says costs fell "up to 30% in the pilot region." Both mention 30%, but the source describes a best case in one region. You'd only see this by reading the quote against the claim. Fix the sentence before it reaches a slide.
Going further
Know the limits of the Citations feature. It works with PDFs, plain text and custom content documents, and scanned PDFs without extractable text can't be cited. It also can't be combined with structured outputs: the API returns a 400 error if you try. In the Claude app, web search answers include citations, though Anthropic notes some links may not work. Rule of thumb, not a vendor figure: Anthropic says projects use retrieval to load only relevant content, so when you need a complete summary of one document, paste it into the chat rather than relying on project knowledge.
Common mistakes
- Checking whether a quote exists and not whether it supports the claim. Read the surrounding sentences.
- Checking the easy details and skipping the one figure your decision depends on.
- Quoting Claude's paraphrase in your own work as if it were the source's words.
- Asking for a citation-backed summary of a scan. Without extractable text, the Citations feature can't cite it.
Sources
- Reduce hallucinations, Claude Platform Docs
- Citations, Claude Platform Docs
- Enabling and using web search, Claude Help Center
- Context window on paid plans, Claude Help Center
Checked 6 November 2026. Products change often, so confirm details with the vendor.