curl --request GET \
  --url https://api.tilt.io/api/v1/custom/org/{organization_uuid}/reports/holdings/ \
  --header 'X-Api-Key: <api-key>'

{
  "total_market_value": "<string>",
  "total_qty": "<string>",
  "num_unique_constituents": 123,
  "num_clients_with_holdings": 123,
  "num_clients_total": 123
}