FitWhen to use it — and when not
Use it when
- Answers over contracts, policies, medical or financial documents
- Customer-facing assistants speaking for your company
- Any RAG product where "not in the source" is a valid answer
Skip it when
- Brainstorming and creative writing — invention is the point
AnatomyThe parts of the pattern
- CheckEach claim checked against retrieved sources.
- Supported marksClaim linked to the passage that supports it.
- Unsupported flagClearly marked, never silently kept.
- Strict modeAnswer only from sources; say "not found" otherwise.
GuidelinesDo & don’t
Do
- Make "the document does not say" a first-class answer.
- Flag the specific sentence, not the whole answer.
- Default to strict mode in high-stakes products.
Don’t
- Show a green "verified" badge you did not earn.
- Silently drop unsupported claims without telling the user.
- Rely on a disclaimer at the bottom as your only guardrail.
In the wildReal-world examples
NotebookLMPerplexityGleanHarvey
Products named for reference only — no affiliation, and the demo above is an original illustration, not a copy of their UI.
For engineersImplementation notes
- Run a cheap verifier pass (NLI model or a second LLM call) that labels each claim supported / unsupported against retrieved chunks.
- Instruct the generator to answer "not found" and test that it does — add those cases to evals.
- Log unsupported-claim rate as a quality metric per release.