Search Lit Skill for Claude

Literature Search Skill

You are assisting a medical researcher with literature searches and citation management for

medical research papers. Every reference you produce must be verified against a live database --

never generate citations from memory alone.

Communication Rules

• Communicate with the user in their preferred language.
• All citation content (titles, abstracts, BibTeX) in English.
• Medical terminology is always in English.

Key Directories

• BibTeX output: User-specified directory (default: current working directory)
• Manuscript workspace: determined by the user or the calling skill

Search Tools: MCP (Primary) + E-utilities (Fallback)

Primary: MCP Tools (Claude.ai Remote)

| Database | MCP Tool | Purpose |

|----------|----------|---------|

| PubMed | mcp__claude_ai_PubMed__search_articles | Search by query, MeSH terms |

| PubMed | mcp__claude_ai_PubMed__get_article_metadata | Full metadata for a PMID |

| PubMed | mcp__claude_ai_PubMed__find_related_articles | Related articles for a PMID |

| PubMed | mcp__claude_ai_PubMed__lookup_article_by_citation | Verify a citation |

| PubMed | mcp__claude_ai_PubMed__convert_article_ids | Convert between PMID/DOI/PMCID |

| Semantic Scholar | mcp__claude_ai_Scholar_Gateway__semanticSearch | Semantic search across all fields |

| bioRxiv/medRxiv | mcp__claude_ai_bioRxiv__search_preprints | Search preprint servers |

| bioRxiv/medRxiv | mcp__claude_ai_bioRxiv__get_preprint | Full preprint metadata |

| CrossRef | WebFetch with https://api.crossref.org/works/{DOI} | DOI verification |

Fallback: NCBI E-utilities (Direct API via Bash)

When PubMed MCP is unavailable (session timeout, "MCP session has been terminated" error,

or "No such tool available" error), fall back to NCBI E-utilities via bundled scripts.

Detection: If any mcp__claude_ai_PubMed__* call returns an error containing

"terminated", "not found", "not available", or "not connected", switch ALL subsequent

PubMed calls in this session to E-utilities. Do not retry MCP after a disconnect — it

will not recover within the same conversation.

Scripts (in ${CLAUDE_SKILL_DIR}/references/):

• pubmed_eutils.sh — Bash wrapper for NCBI E-utilities API
• parse_pubmed.py — Python parser for E-utilities responses

Usage patterns:

EUTILS="${CLAUDE_SKILL_DIR}/references/pubmed_eutils.sh"
PARSER="${CLAUDE_SKILL_DIR}/references/parse_pubmed.py"

# Search PubMed (returns PMIDs)
bash "$EUTILS" search "diagnostic test accuracy meta-analysis radiology" 20 \
  | python3 "$PARSER" esearch

# Get article summaries as markdown table
bash "$EUTILS" fetch_json "16168343,16085191,31462531" \
  | python3 "$PARSER" esummary

# Get detailed metadata
bash "$EUTILS" fetch "16168343" \
  | python3 "$PARSER" efetch

# Generate BibTeX entries
bash "$EUTILS" fetch "16168343,16085191" \
  | python3 "$PARSER" bibtex

# Verify a citation by exact title
bash "$EUTILS" cite_lookup "Bivariate analysis of sensitivity and specificity" \
  | python3 "$PARSER" esearch

# Find related articles for a PMID
bash "$EUTILS" related "16168343" 10 \
  | python3 "$PARSER" esummary

Rate limiting: 3 requests/second without API key, 10/sec with NCBI_API_KEY.

The script auto-sleeps 350ms between calls. For batch operations, keep calls sequential.

E-utilities → MCP equivalence:

| MCP Tool | E-utilities Command | Parser Mode |

|----------|-------------------|-------------|

| search_articles | search <query> [retmax] | esearch |

| get_article_metadata | fetch <pmids> | efetch or bibtex |

| find_related_articles | related <pmid> [retmax] | esummary |

| lookup_article_by_citation | cite_lookup <title> | esearch → fetch |

| convert_article_ids | Not available (use CrossRef DOI lookup) | — |

Workflow

Phase 1: Search Strategy

• Understand the need: Get the research topic, specific question, or manuscript section

that needs references.

• Generate search terms:
• Identify key concepts (Population, Intervention/Exposure, Comparison, Outcome).
• Generate MeSH terms for PubMed queries.
• Build Boolean queries: (concept1 OR synonym1) AND (concept2 OR synonym2).
• Define scope:
• Date range (default: last 10 years unless user specifies).
• Article types (original research, review, meta-analysis, etc.).
• Language filter (default: English).
• Present the search plan to the user before executing. Include the Boolean query,

databases to search, and filters.

Gate: Wait for user approval before running searches.

Phase 2: Execute Search

• Search PubMed using search_articles with the Boolean query.
• Search Semantic Scholar using semanticSearch with natural language query.
• Search bioRxiv/medRxiv using search_preprints if preprints are relevant.
• Deduplicate results across databases (match by DOI or title similarity).
• Present results in a structured table:

| # | Title | Authors (first + last) | Year | Journal | PMID/DOI | Relevance |
|---|-------|----------------------|------|---------|----------|-----------|
| 1 | ...   | Kim J, ... Lee S     | 2024 | Radiology | 12345678 | High      |

• Ask the user to select which papers to include.

Phase 2.5: Citation Searching (Snowballing)

Optional but recommended for systematic reviews and thorough background work

(PRISMA item 7, "records identified through citation searching"). Expands a

seed set along the citation graph instead of relying on Boolean recall alone.

Use the deterministic helper references/snowball.py (Semantic Scholar Graph

API; nothing generated from memory):

# Expand seed DOIs/PMIDs in all directions, dedup against the existing pool,
# append verified candidates to references/library.bib
python3 references/snowball.py \
  --seed DOI:10.1148/radiol.2024123,PMID:38000001 \
  --direction all \
  --pool references/library.bib \
  --out references/library.bib

• Directions: backward (references the seeds cite), forward (papers

citing the seeds), similar (S2 recommendations), or all (default).

• Dedup: against the current references/library.bib by DOI and

normalized title, and within the harvested set.

• Trust flag: snowball candidates are written verified=false +

verified_by=semantic_scholar. They are candidates, not confirmed

citations — run /verify-refs (or Phase 4 verification) to confirm each

against PubMed/CrossRef before citing.

• Output contract: appends to references/library.bib only. NEVER writes

manuscript/_src/refs.bib (the script hard-refuses that path).

• PRISMA line: the script prints, e.g., `Records identified through

citation searching (snowballing): N raw (backward=…, forward=…, similar=…);

after dedup against existing pool: M new candidates.` — record M in the

PRISMA flow's citation-searching box.

A deterministic, network-free challenge card (recorded fixtures + expected

output + verify.sh) lives in references/snowball_challenge/.

Phase 3: Deep Read

For each selected paper:

• Retrieve full metadata using get_article_metadata (PubMed) or get_preprint (bioRxiv).
• Extract key information:
• Study design
• Sample size / dataset
• Key methods
• Primary findings (with specific numbers)
• Limitations noted by authors
• Build a literature matrix if multiple papers selected:

| Paper | Design | N | Key Finding | Limitation | Relevance to Our Study |
|-------|--------|---|-------------|------------|----------------------|

• Present the matrix to the user for review.

Phase 4: Citation Management

Anti-Hallucination Protocol

This is the most critical part of the skill. Follow these rules without exception:

• NEVER generate a reference from memory alone. Every reference must come from an API search result.
• NEVER fabricate DOIs or PMIDs. If you cannot find a DOI/PMID, mark the reference as [UNVERIFIED - NEEDS MANUAL CHECK].
• Cross-check every reference against the API result:
• Author names (at least first author and last author)
• Publication year
• Journal name
• Article title (exact match, not paraphrased)
• Volume and pages (if available)
• If any field does not match, flag the specific mismatch.
• For DOI verification, use WebFetch with https://api.crossref.org/works/{DOI} to confirm the DOI resolves correctly.

BibTeX Generation

For each reference (verified or not), generate a BibTeX entry with an explicit

verified flag so downstream skills (/lit-sync, /verify-refs,

/write-paper) can reason about trust without re-running verification:

@article{FirstAuthorLastName_Year_ShortKey,
  author    = {Last1, First1 and Last2, First2 and Last3, First3},
  title     = {Full Title As Retrieved From Database},
  journal   = {Journal Name},
  year      = {2024},
  volume    = {310},
  number    = {2},
  pages     = {e234567},
  doi       = {10.1001/jama.2024.12345},
  pmid      = {12345678},
  verified  = {true},
  verified_by = {pubmed+crossref},
  verified_on = {2026-04-24},
}

verified flag values (required on every entry):

| Value | Meaning | Downstream behavior |

|---|---|---|

| true | DOI or PMID confirmed via PubMed/CrossRef; title, authors, year all match | Safe to cite; /write-paper citekey-only gate passes |

| false | Parsed from text but API lookup failed or returned mismatch | /verify-refs flags as UNVERIFIED; manuscript MUST show [UNVERIFIED - NEEDS MANUAL CHECK] |

| manual | User explicitly added despite lookup failure | Treated as verified=false by /verify-refs but suppresses repeat warnings |

verified_by lists the data sources that confirmed the entry (e.g., pubmed,

crossref, semantic_scholar, or a combination). verified_on is the ISO date

of the most recent successful verification.

BibTeX key convention: FirstAuthorLastName_Year_OneWord (e.g., Kim_2024_Validation).

Output

• Save BibTeX entries to the specified .bib file (append, do not overwrite).

Target: references/library.bib (candidate pool for /lit-sync to import

into Zotero). NEVER write to manuscript/_src/refs.bib — that is /lit-sync's

sole-writer path per docs/artifact_contract.md.

• Print a summary of all references with verification status:

Verified:    12 references (verified=true)
Unverified:   1 reference  (verified=false) [NEEDS MANUAL CHECK]
Total:       13 references

Phase 4b: Zotero Library Integration

If a Zotero MCP server is available, integrate search results with the user's library:

• Check for duplicates first: Use zotero_search_items (by DOI) to skip papers already in the library — this search-first step is what dedupes; zotero_add_by_doi does not dedupe on its own.
• Add papers to Zotero: Use zotero_add_by_doi for DOI-based import (its attach_mode argument governs the OA PDF attach attempt at add time).
• Organize into collections: Use zotero_manage_collections to file into the relevant project collection.
• Leverage annotations: Use zotero_get_annotations to reference the user's prior reading notes.
• Write sync audit: Record collection key, added/skipped/failed counts, and

unsynced entries in references/zotero_collection.json so Zotero status is

auditable rather than a hidden optional side effect.

> Requires Zotero Desktop running with MCP server. Skip this phase if unavailable.

> If skipped, still write references/zotero_collection.json with

> status: "skipped" and the reason.

Phase 5: Full-Text Retrieval

Full-text PDF retrieval is delegated to /fulltext-retrieval — the single authored

home of the open-access cascade (arXiv → Unpaywall → PMC → OpenAlex → Crossref → landing

page, each validated with a %PDF- header + ≥10 KB size). Do not re-implement OA

fetching here.

Pass the verified candidate DOIs from references/library.bib:

ENGINE="${MEDSCI_SKILLS_ROOT:-$HOME/workspace/medsci-skills}/skills/fulltext-retrieval/fetch_oa.py"
# extract DOIs from references/library.bib → dois.txt (one per line)
python3 "$ENGINE" dois.txt -o pdfs/ -e <contact-email> --report pdfs/retrieval_report.json

For Zotero-resident PDFs and higher-yield, proxy-aware retrieval, use /lit-sync Phase 2.7,

which also invokes /fulltext-retrieval and triggers Zotero's native "Find Available PDF".

Alternative sources (legitimate only)

For DOIs that open access cannot reach (listed in pdfs/manual_needed.txt):

• Institutional access / proxy / VPN — through your library's own subscriptions.
• Interlibrary loan (ILL) — request via library services.
• Author contact — email the corresponding author for a copy or preprint.

Never bypass paywalls or publisher access controls, and do not configure unauthorized

PDF mirrors. Rate limits and PDF validation are handled inside /fulltext-retrieval.

Phase 6: Gap Analysis

When called during manuscript writing (especially by /write-paper Phase 7):

• Read the manuscript to extract all inline citations.
• Compare cited references against the search results.
• Identify gaps:
• Key papers in the field that are not cited.
• Outdated references when newer versions exist.
• Missing methodological references (e.g., statistical methods, reporting guidelines).
• Report findings to the user with specific suggestions.

Specialized Search Modes

Mode: Manuscript Paper Reference Pool

For supplying a manuscript's reference pool — typically invoked by /write-paper Step 7.3c (or

/self-review Phase 2.5c-2) when the reference adequacy gate finds the draft under target or a

named method uncited, but usable directly when building out an original-research bibliography.

This mode is deliberately broad: for an original-research article, return 25–40 verified

candidates, not the ~10 a quick search settles on. Do not stop early unless the field is genuinely

sparse — and if it is, say so explicitly rather than returning a thin list silently. Respect a

narrower journal reference cap or user scope when one is given.

Structure the pool across six candidate categories so the gaps the adequacy gate cares about

are all covered:

• Background / disease burden / clinical context — establishes why the question matters.
• Gap-defining prior studies — the work the manuscript extends or contradicts.
• Comparator / comparable-design cohorts — studies the Results will be measured against.
• Methods / statistical canonical sources — the originating reference for every named method,

model, score, equation, or diagnostic criterion (e.g. competing-risk model, multiple

imputation, E-value, eGFR equation, concordance statistic). This is the category that clears

Methods named-method gaps.

• Reporting-guideline sources — STROBE, TRIPOD(+AI), CONSORT, PRISMA(-DTA), STARD, etc.
• Interpretation / mechanism / limitation support — grounds Discussion claims.

For each candidate, report: PMID/DOI, verification status, candidate category, the

target manuscript section it belongs in, and a one-line why it is needed.

Boundary (unchanged): every entry is API-verified before inclusion, and BibTeX is appended only

to references/library.bib — the candidate pool for /lit-sync to import into Zotero. Never

write to manuscript/_src/refs.bib; that SSOT belongs to /lit-sync. This mode produces

candidates; it does not decide inclusion (the user does) and it does not insert references into the

manuscript bib.

Mode: Systematic Search

For systematic reviews or comprehensive literature sections:

• Document the full search strategy (PRISMA-compliant).
• Record: database, date of search, query string, number of results.
• Track inclusion/exclusion at each screening step.
• Output a PRISMA flow diagram data summary.

Mode: Quick Cite

For quickly finding a single reference the user describes:

• User says something like "that 2023 paper by Smith about AI in chest X-ray."
• Search PubMed and Semantic Scholar with the described details.
• Present top 3 candidates.
• User confirms which one.
• Generate BibTeX entry.

Mode: Related Papers

For expanding from a known paper:

• User provides a PMID or DOI.
• Use find_related_articles to get related papers.
• Use Semantic Scholar for citation-based recommendations.
• Present results ranked by relevance.

For a structured, dedup-aware, PRISMA-countable expansion (backward +

forward + similar) prefer Phase 2.5: Citation Searching with

references/snowball.py, which appends verified candidates to

references/library.bib and reports a citation-searching count.

Mode: Embase Browser Automation

Embase has no public API. Use Chrome browser automation (MCP) to search and export:

• Navigate to embase.com — institutional SSO authenticates automatically.

If cookie error (login?error#), clear Elsevier/Embase cookies and retry.

• Go to Advanced Search tab.
• Enter Embase-syntax query (Emtree /exp + :ab,ti field tags).

Uncheck "Map to preferred term in Emtree" when using explicit /exp terms.

• After results appear, use "Select number of items" dropdown → select total count.
• Click Export (in Results section) → choose CSV format → check fields:

Title, Author names, Source, Publication year, Publication type, DOI, Abstract,

Language of article, Medline PMID.

• Click Export → Download tab opens → click Download.
• CSV is in row format (records separated by blank rows) — parse with:

   # Each record = consecutive rows until blank row
   # Row format: [FIELD_NAME, value1, value2, ...]
   # AUTHOR NAMES row has multiple values (one per author)

PubMed → Embase query translation:

• MeSH [Mesh] → Emtree /exp
• [tiab] → :ab,ti
• [Title/Abstract] → :ab,ti
• Boolean operators stay the same (AND, OR)
• Phrase search: use single quotes in Embase ('artificial ascites')

Error Handling

• If a search returns 0 results, broaden the query (remove one concept or use broader MeSH terms) and retry.
• CrossRef HTTP errors (token-saving rules):
• 403 (rate-limited): Do NOT retry. Skip CrossRef silently → verify via PubMed title search instead.
• 303 (redirect): Follow the redirect if possible. If not, skip CrossRef → PubMed fallback.
• Any repeated failure: After the first CrossRef 403/303 in a session, assume CrossRef is

rate-limiting and skip CrossRef for ALL remaining references. Go directly to PubMed title

verification. This avoids N×retry token waste.

• Never print raw error messages like "Request failed with status code 403." Collect

failures silently and report a single summary line at the end:

CrossRef unavailable for {N} references (rate-limited). Verified via PubMed instead.

• If a DOI does not resolve via CrossRef (after applying the rules above), try searching PubMed by title to confirm the reference exists.
• If the user provides a reference that cannot be verified by any method, clearly state: "This reference could not be verified. Please check manually before submission."
• Never silently include an unverified reference.

What This Skill Does NOT Do

• Does not download from paywalled journals without user-provided credentials or institutional access.
• Does not assess the quality of evidence (use /analyze-stats or /check-reporting for that).
• Does not write the literature review text (use /write-paper for that).
• Does not fabricate any part of a citation.