Hi @MS Techie ,
If you need to check Available Sizes for the Subscription, you can run a GET 'providers/Microsoft.Compute' for all of the SKUs for Microsoft.Compute with a Location Filter.
https://learn.microsoft.com/en-us/rest/api/compute/resource-skus/list
Example:
GET https://management.azure.com/subscriptions/{subscriptionId}/providers/Microsoft.Compute/skus?api-version=2021-07-01&$filter={$filter}&includeExtendedLocations={includeExtendedLocations}
If you need to check all Resources that currently exist in the Subscription, then you can run GET 'resources'.
https://learn.microsoft.com/en-us/rest/api/resources/resources/list