Stop Asking the LLM Whether Its Source Is Real
You ask the AI for a bibliography. It hands you a title, authors, a journal, a year, a well-formed DOI. Everything is plausible, everything is clean. And one reference in two doesn't exist. Not "approximate": nonexistent. The DOI resolves to nothing, the paper was never written. The reflex is to ask the model again: "are you sure this source is real?" It says yes. Always. You just asked the forger about the authenticity of his forgery. Hallucination is plausible by construction An LLM doesn't store a database of publications. It generates likely sequences of words. A citation, to it, is a shape: a surname, an initial, two more names, a capitalized journal, a recent year, ten DOI digits. It produces that shape perfectly, because that's exactly what it's good at. The content doesn't need to be true to be plausible, it just needs to resemble. That's why a hallucinated reference is so vicious: it doesn't look like an error. A wrong calculation jumps out. An invented citation looks like a real one, until you click. Don't ask the culprit The golden rule fits in one sentence: never ask the model that hallucinated a citation whether that citation is real. For two reasons that compound. First, it doesn't have the information: it has no access to a registry, it can only regenerate something plausible. Second, even if it doubted, its self-evaluation bias pushes it to confirm what it already produced. You get a "yes" worth nothing. Verification has to come from elsewhere. From a source the model neither controls nor can invent: a metadata API. Three filters: existence, credibility, fidelity In my pipeline for writing technical dossiers, no reference enters the document before clearing three filters, in this order. Existence. The DOI must resolve. It's binary, and it's free. Crossref exposes its whole database: curl -s "https://api.crossref.org/works/10.1145/3290605.3300233" \ | jq '.message.title[0], .message.author[0].family, .message["published"]' If the API returns a title a