PubMed Trends (x402) is an API that delivers publication-level trend analytics derived from PubMed searches. It provides endpoints for hottest-topic spike detection, daily publication pulse with multiple rolling windows and year-over-year changes, single-year snapshots, emerging-topic detection, multi-term comparisons, and multi-year trend series. Use it to power dashboards, alerts, literature scouting, bibliometric reports, and research strategy tools.