Re: The description of the GatewayNatRuleType is not returned

You are trying to set NatRuleType instead of GatewayNatRuleType

GatewayNatRuleType is for Gateway NAt service and does not have description

Here is schema for both NAtRuleType and GatewyaRuleType:

<NatRuleType xmlns="http://www.vmware.com/vcloud/v1.5">
     <Description> xs:string</Description>
     <RuleType> xs:string</RuleType>
     <IsEnabled> xs:boolean</IsEnabled>
     <Id> xs:int</Id>
</NatRuleType>

<GatewayNatRuleType xmlns="http://www.vmware.com/vcloud/v1.5">
     <Interfacehref="xs:anyURI" id="xs:string" name="xs:string" type="xs:string"/>
     <OriginalIp> IpAddressType</OriginalIp>
     <OriginalPort> xs:string</OriginalPort>
     <TranslatedIp> IpAddressType</TranslatedIp>
     <TranslatedPort> xs:string</TranslatedPort>
     <Protocol> xs:string</Protocol>
     <IcmpSubType> xs:string</IcmpSubType>
</GatewayNatRuleType>