curl --request GET \
  --url https://xbt-mainnet.gomaestro-api.org/v0/rpc/block/{height_or_hash}/volume \
  --header 'api-key: <api-key>'

{
  "data": {
    "total_output_satoshis": 123
  },
  "last_updated": {
    "block_hash": "<string>",
    "block_height": 123
  }
}