How do I get constructor Id and ObjectPathId for a webservice in Sharepoint 2013?

I'm trying to test the following WebService endpoint

/_vti_bin/http://ift.tt/WVHpI8 

With the following query.

<Request AddExpandoFieldTypeSuffix="true" SchemaVersion="15.0.0.0" LibraryVersion="16.0.0.0" ApplicationName=".NET Library"
xmlns="http://ift.tt/Yw5aqy">
<Actions>
    <ObjectPath Id="263" ObjectPathId="262" />
    <ObjectPath Id="265" ObjectPathId="264" />
    <Query Id="266" ObjectPathId="264">
        <Query SelectAllProperties="false">
            <Properties>
                <Property Name="IsSiteAdmin" ScalarProperty="true" />
                <Property Name="Title" ScalarProperty="true" />
                <Property Name="LoginName" ScalarProperty="true" />
                <Property Name="PrincipalType" ScalarProperty="true" />
                <Property Name="Groups" SelectAll="true">
                    <Query SelectAllProperties="false">
                        <Properties />
                    </Query>
                </Property>
            </Properties>
        </Query>
    </Query>
</Actions>
<ObjectPaths>
    <Constructor Id="262" TypeId="{268004ae-ef6b-4e9b-8425-127220d84719}" />
    <Method Id="264" ParentId="262" Name="SetSiteAdmin">
        <Parameters>
            <Parameter Type="String">http://ift.tt/1C0adAg;
            <Parameter Type="String">blabla@tenantName@onmicrosoft.com</Parameter>
            <Parameter Type="Boolean">true</Parameter>
        </Parameters>
    </Method>
</ObjectPaths>

This is actually taken from Fiddler, I was using Powershell and wanted to do it via Webservice myself.

How does Powershell get/construct these values? Can I construct them or get them or get them through any webservice?