curl --request GET \
  --url https://api.asksurf.ai/gateway/v1/prediction-market/category-metrics

{
  "data": [
    {
      "category": "<string>",
      "notional_volume_usd": 123,
      "open_interest_usd": 123,
      "source": "<string>",
      "subcategory": "<string>",
      "timestamp": 123
    }
  ],
  "meta": {
    "cached": true,
    "credits_used": 123,
    "limit": 123,
    "offset": 123,
    "total": 123
  },
  "$schema": "<string>"
}