Citation Verifier

Overview

Use this skill when citation integrity is the bottleneck. It is narrower and more operational than general writing skills: the goal is to catch unverifiable references, missing identifiers, duplicated BibTeX keys, placeholder citations, and mismatches between local citation artifacts before they become submission problems.

Use this skill together with scientific-writing or submission-audit, not instead of them.

This is stage one of three. It shows the bibliography is well-formed; it cannot show that the cited papers are real, and it cannot show that a real paper supports the sentence citing it. Hand the surviving entries to reference-audit-guide (optional set, installed with --set all), which queries CrossRef, Semantic Scholar, arXiv, and PubMed to confirm existence and match metadata, then to claim-source-verification for claim-to-evidence support. When reference-audit-guide is not installed, say that existence was not machine-verified rather than letting a clean local scan stand in for it. A fabricated citation carrying a well-formed DOI passes this skill and fails the next one.

When To Use

Use this skill when:

• a manuscript is close to submission or resubmission
• the bibliography may contain placeholders, guessed entries, or stale metadata
• a .bib file needs a hygiene pass
• the draft mixes DOI, arXiv, PMID, or plain-text references inconsistently
• you need to verify that local citation artifacts are ready before manual or online source verification

Do not use this skill for:

• generic literature discovery from scratch
• full manuscript restructuring
• venue formatting that does not depend on citation integrity

Local First Pass

Start with a local citation scan before any online verification.

The helper script:

python ~/.agents/skills/citation-verifier/scripts/scan_citations.py path/to/file_or_dir [...]
# Claude Code (global install): replace ~/.agents/skills with ~/.claude/skills
# Claude Code (project-local install): replace ~/.agents/skills with .claude/skills

Use it to find:

• [CITATION NEEDED] or similar placeholders
• PLACEHOLDER_... citation keys
• TODO: verify markers
• DOI, arXiv, and PMID tokens
• LaTeX \cite{...} keys
• duplicate BibTeX keys inside .bib files

Treat imported BibTeX and Google Scholar-style exports as draft metadata, not as verified truth.

Verification Order

1. Scan the local draft and bibliography artifacts.
2. Remove or flag all placeholder citations.
3. Check BibTeX-key uniqueness and obvious identifier gaps.
4. Normalize metadata fields that are commonly wrong in copied BibTeX:
   • author list and spelling
   • year
   • venue or journal name
   • volume, issue, pages, or article number
   • DOI versus preprint identifier
5. For every citation that matters to a scientific claim, verify the paper exists in trusted sources.
6. If a claim depends on a specific result, confirm the cited paper actually supports that claim. For a systematic pass over many such claims, hand off to claim-source-verification: existence and metadata checks do not catch a real paper made to carry a conclusion it does not reach.
7. Only then finalize formatting for the venue.

Severity Grading

When you report field-level mismatches, grade each one so authors fix the dangerous ones first:

• Critical (must fix): wrong or fabricated first author, reversed author order, a DOI that resolves to a different paper, a title whose core terms do not match, or a page range off by five or more.
• Warning (verify): volume-year inconsistent with the DOI-registration year, a missing or extra issue number, a missing middle initial, a page range off by one to four, or an ambiguous publisher-name variant.
• Info (note only): title case versus sentence case, abbreviated versus full journal name, and punctuation or conjunction differences (and versus &).

Two checks are easy to miss and worth running explicitly:

• Volume-year versus DOI-year: a citation whose stated volume-year differs from the year encoded in the DOI or the online-publication date is a common sign of a miscopied entry.
• Author-order reversal: verify the first author specifically, not just that all names are present; a reversed or shifted author list still passes a set-membership check.

Roll each reference up to one confidence verdict: verified, check_suggested (has a Warning), needs_fix (has a Critical), or unverifiable (no source could confirm it).

Trusted Verification Sources

Prefer this order when moving beyond local scans:

• publisher page or DOI resolver
• PubMed for biomedical papers
• arXiv for preprints
• Crossref or Semantic Scholar for metadata cross-checking
• Google Scholar only as a fallback discovery aid, not as the sole source of truth

Common Failure Modes

• writing BibTeX from memory
• leaving placeholder citation keys in the draft
• assuming an arXiv preprint and published version are interchangeable
• citing a paper correctly but using it to support a claim it does not make
• letting duplicate BibTeX keys silently overwrite entries
• blindly trusting copied Scholar or BibTeX metadata for venue names, pages, years, or DOI fields

Output Standard

When using this skill, report:

• placeholder or unverifiable items
• duplicate or suspicious BibTeX keys
• missing or inconsistent DOI/arXiv/PMID information
• suspicious metadata fields that need manual correction
• claims that still need source verification
• the minimum safe next step before submission