Check a single DOI against Crossref for retraction, correction, or expression-of-concern status. Use this before citing a paper in a document, summary, or literature review -- retracted papers (including fraudulent or debunked ones) continue to be cited for years after retraction, often because whoever is citing them has no easy way to check. This tool checks three independent signal sources: publisher-asserted updates, Crossref's ingested Retraction Watch data (which catches many retractions the publisher's own metadata misses), and a title-prefix fallback ("RETRACTED:", etc.) for older or unlinked cases.

Args:

• doi (string): a DOI, with or without a "https://doi.org/" prefix.

Returns: For JSON format: { "doi": string, "verdict": "retracted" | "concern" | "corrected" | "clean" | "not_found" | "error", "title": string | null, "signals": [ { "type": string, "source": string, "label": string | null, "noticeDoi": string | null, "date": string | null } ], "error": string | null }

Examples:

• Use when: about to cite a paper in a summary, report, or literature review -- check it first

• Use when: reviewing someone else's bibliography for outdated or unreliable sources

• Don't use when: you need to verify a claim's accuracy generally -- this only checks retraction status, not whether the paper's content is correct

Error Handling:

• A DOI Crossref doesn't recognize returns verdict "not_found", not an error -- it may still be a real paper Crossref just doesn't index (e.g. some preprints), not necessarily an invalid citation.

Extract every DOI found in a block of text (a reference list, a paper draft, an exported bibliography) and check each one for retraction/correction/expression-of-concern status via Crossref. Use this to sanity-check a whole reference list at once before finalizing a document, rather than checking citations one at a time.

Finds DOIs in any form: bare ("10.1016/S0140-6736(97)11096-0"), as a doi.org URL, or embedded in a formatted citation. Up to 50 unique DOIs are checked per call; if more are found, only the first 50 (in order of first appearance) are checked and the response says so.

Args:

• text (string, 1-200000 chars): the text to scan.

Returns: For JSON format: { "totalFound": number, "checked": number, "truncated": boolean, "results": [ { "doi": string, "verdict": string, "title": string|null, "signals": [...], "error": string|null } ] }

Examples:

• Use when: finishing a literature review or research summary -- paste the whole reference list to check it in one call

• Don't use when: checking just one citation you already have the DOI for -- use check_citation instead, it's simpler

Error Handling:

• Returns an error if text is empty or exceeds 200000 characters. Text with no DOI-shaped substrings returns totalFound: 0, not an error.