1. https://www.zabbix.com/documentation/5.0/manual/api/changes_4.4_-_5.0
SNMP setting was transferred from items(in 4.0) to interfaces(in 5.0). Details section(which describes SNMP setting) was added to all hostinterface methods, not only to hostinterface.get.
Also would be nice to add Example of such interface creation to hostinterface.create method documentation. Example below:

{
    "jsonrpc": "2.0",
    "method": "hostinterface.create",
    "params": {
        "hostid": "10456",
        "main": "0",
        "type": "2",
        "useip": "1",
        "ip": "127.0.0.1",
        "dns": "",
        "port": "1601",
        "details": {
            "version": "2",
            "bulk": "1",
            "community": "{$SNMP_COMMUNITY}"
        }
    },
    "auth": "038e1d7b1735c6a5436ee9eae095879e",
    "id": 1
}

It will save time to create it for first time.

2. https://www.zabbix.com/documentation/5.0/manual/api/reference/hostinterface/object
To create SNMP interface for version 1 and 2c "community" field is REQUIRED! Without it API will get response : "Incorrect arguments passed to function." Which is not self explanatory.
In documentation confusion comes from word used. It is better to change to required