Wikipedia summary API: the lead summary of any English Wikipedia article — title, one-line description, extract paragraph, thumbnail, canonical URL, and Wikidata item id; disambiguation pages labeled via 'kind'. Titles case-sensitive; spaces or underscores accepted. Content CC BY-SA 4.0 with attribution in meta.attribution of every response. Use for knowledge lookup, entity enrichment, and fact grounding by agents. Cached up to 24 hours.