search-lit

# 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:**

```bash
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

1. **Understand the need**: Get the research topic, specific question, or manuscript section
   that needs references.
2. **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)`.
3. **Define scope**:
   - Date range (default: last 10 years unless user specifies).
   - Article types (original research, review, meta-analysis, etc.).
   - Language filter (default: English).
4. **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

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

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

6. 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):

```bash
# 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/libra