`/v1/advisories/summary` — canonical advisory counts by headline severity band. This is the purpose-built aggregate behind browse summary tiles: it reuses the browse list's canonical universe (rollups joined back to their source records) and its headline-score bounds, but skips the per-group display metadata, search, sorting, and windowing that make the full browse query expensive, so callers no longer issue several `limit=1` browse requests just to read totals.

curl -X GET "https://example.com/v1/advisories/summary"

{  "critical": 0,  "high": 0,  "low": 0,  "medium": 0,  "total": 0,  "unscored": 0}