curl --request POST \
  --url https://sandbox.groundtech.co/v2/address-book/entries \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "address": "0x52908400098527886E0F7030069857D2E4169EE7",
  "chain": "arbitrum",
  "label": "Ops treasury"
}
'

{
  "entry": "<unknown>"
}