Least-privilege SharePoint access for AI indexers: Microsoft Graph Sites.Selected in practice

An AI assistant that answers from SharePoint needs two identities: an indexer that reads documents on a schedule with nobody signed in, and an answering service that acts for the person asking. Vendors often request the tenant-wide application permission Sites.Read.All, which makes their setup easier but is not a technical requirement of the indexer. This technical note summarises, from Microsoft documentation and from the indexer we run, how the indexer can be limited to named sites with Microsoft Graph Sites.Selected and the read role, why the answering service should never hold the indexer's credential (certificate in Azure Key Vault, temporary grant app removed after use), and how an administrator can check that a site outside the list is really denied. Full article with all citations: https://ksj.lv/en/sharepoint-ai-indexer-permissions-sites-selected/