Glossary
Citation
A citation is the link or reference an answer offers as the source of a claim, which tells you where something is said to have come from and becomes evidence only once somebody opens it.
In plain terms
A pointer, not a proof. It says here is where this came from, and whether the page it points at actually says that is a separate question with a separate answer. Following two of them takes you a minute, and it is the difference between an answer you can forward and one you merely hope is right.
Why it matters
Citations changed how these tools feel far more than how reliable they are. An answer with numbered links looks checkable and reads as more trustworthy to you, which is exactly the effect that makes not checking easier. The value is entirely real and entirely conditional: it exists once somebody follows the link, and until then a marker is a promise rather than a fact.
How it works
The system fetched something before answering and attached a reference to the material it drew on. That is the honest version, and the looseness lives in drew on: a passage can inform a sentence without supporting the specific claim attached to it, and nothing in the format distinguishes those two cases.
Failures come in a few recognisable shapes. A link that does not resolve at all, a page that exists but says something different, a real source cited for a claim it does not make, and a sentence with no marker sitting comfortably among sentences that have one. The last is the one worth watching for, and the hardest to notice.
Where a system was told to answer only from supplied material, the citations should point inside it, and checking a couple confirms whether the instruction held. Where a system searched the web, the citations point outward and inherit whatever the source was worth, so a confidently wrong page hands you a confidently wrong answer with a working link attached.
Reading for absence is the more useful habit. Scanning an answer for the sentences carrying no marker takes you seconds, and those are where a model's own recall crept into material that was otherwise sourced. It is a quicker and better check than following every reference.
What a marker tells you, and what it does not
Seen in the wild
Follow the numbered links on a research answer back to the pages themselves and check whether each page actually says the sentence it is attached to.
PerplexityAsk a notebook tool something its sources do not cover and see whether it says so or produces an answer with no marker on it.
NotebookLMSearch a company workspace and follow an answer back to the document, which is the same check applied to material only colleagues can see.
Glean
Common misconceptions
People assume
An answer with citations has been checked.
In fact
It has been sourced, by software, which is a different claim. Whether each source supports the sentence attached to it is a question only reading answers. Treat markers as an invitation to verify rather than as evidence that somebody already did, particularly on anything you intend to forward.
People assume
A real, working link means the claim is right.
In fact
It means a real page exists. Whether that page says what the answer says it says, and whether the page itself is any good, are two further questions. A working link to a confidently wrong source produces a confidently wrong answer that survives every check short of reading it.
Telling them apart
Citation vs Grounding
Citation
The label on the output: a marker pointing at where a statement is said to have come from.
The arrangement behind it: what was fetched, what the model was told to do with it, and what happens when the material falls short.
Signage and plumbing. A product can install the signage without the plumbing, which is why a numbered link is where checking starts rather than where it ends.
Questions
- How many should I actually check?
- Two, on any answer you intend to act on, chosen from the claims that would matter most if they were wrong. Then scan for sentences carrying no marker at all. That takes about a minute and catches the great majority of what goes wrong, which is more than checking every link and then forwarding the whole thing.
- Why do some sentences have no citation?
- Because they came from the model's own recall rather than from retrieved material, which is normal in most products and almost never flagged. Those sentences inherit the credibility of the sourced ones around them, which is why they are worth finding deliberately rather than assuming the whole answer was sourced.
- Can I use a cited answer in something official?
- Only after reading the sources yourself, at which point what you are relying on is the source rather than the answer. That is a perfectly good use of the tool: it found the material quickly. What it has not done is take responsibility for the claim, and no citation format transfers that.
Key takeaways
- A citation says where something came from and does not confirm that the source supports it.
- The failure worth watching for is a sentence with no marker among sentences that have one.
- Reading for absent markers is quicker and more revealing than following every present one.
- An outward-pointing citation inherits whatever the source was worth, including nothing.
- Check two that matter, then scan for the unsourced ones.
Tools that use this
- Perplexity
Numbered links back to pages, which makes the checking habit cheap.
- NotebookLM
Sources you supplied, so an unsourced sentence stands out.
- Glean
The same check over material only colleagues can see.
Last checked July 2026