Hi Dawn, great question — this is a common challenge when aggregating Azure Advisor recommendations across multiple subscriptions.
Currently, the native Advisor REST API (/providers/Microsoft.Advisor/recommendations) does indeed scope results per subscription. However, you can automate cross-subscription retrieval by using an Azure Management Group context or a lightweight script that loops through each subscription via the Azure Resource Graph API.
Resource Graph is much faster and lets you query recommendations at scale using Kusto Query Language (KQL). You can also schedule it via Azure Automation Runbooks or Logic Apps to collect and centralize recommendations periodically.
Microsoft has hinted at a unified Advisor Datalink API in preview, but as of now, the scalable route is using Resource Graph or ARM templates with a management group query layer.
Hope that helps streamline your process a bit!