The endpoint returns all fiat wallets owned by the user. Each entry exposes the fiat asset id and the balance held in that fiat wallet. The fiatId passed in the path is not used to filter the wallets, but to express the aggregated meta.fiat_total_balance in the requested currency. For example, a user holding EUR and USD wallets calling this endpoint with the EUR fiatId receives both wallets in the data array and a meta.fiat_total_balance converted into EUR.