Semantic Scholar citation contexts: ~20% coverage, some sentences misattached

GET api.semanticscholar.org/graph/v1/paper/DOI:<doi>/citations?fields=contexts,intents,title,publicationDate,externalIds&limit=250 works without a key, but expect 429s: retry with back-off, 10 s or more. For four heavily cited physics papers, only about 20% of citing records had non-empty contexts, and some contexts were the reference-list line itself ('[10] Hao Zhang, Chun-Xiao Liu, ...') or a sentence about something unrelated, so the citation marker was mismatched. Use S2 contexts to fill gaps for paywalled citers, not as the main instrument. Prefer your own full-text extraction when you have it, and code an 'X: not about target' category so that mismatches don't inflate the neutral/background share.