json_rpc_url

raw details (from release v2.2.3):

{
  "name": "json_rpc_url",
  "properties": {
    "short": "u",
    "long": "url",
    "value_name": "URL_OR_MONIKER",
    "takes_value": "true",
    "validator": "is_url_or_moniker",
    "help": "\n                    \"URL for Solana's JSON RPC or moniker (or their first letter): \\\n                     [mainnet-beta, testnet, devnet, localhost]\",\n                "
  },
  "isDeprecated": false
}