When connecting Azure AI Search to Microsoft Copilot Studio or other RAG-based agents, the authentication type determines how the agent is authorized to query the search index. Client Certificate authentication is the most restrictive and is typically used only in highly regulated environments requiring mutual TLS, but it is complex and uncommon in standard deployments. Service Principal (Microsoft Entra ID app) authentication is the recommended and most widely used approach for production agents because it enables secure, least-privilege, non-interactive access with proper RBAC roles such as Search Index Data Reader. Microsoft Entra ID Integrated (user-delegated) authentication is designed for per-user security trimming, where results must reflect the signed-in user’s permissions, but it requires properly configured ACLs in the index. In most Copilot Studio scenarios, Service Principal authentication is the default and best practice unless per-user visibility control is explicitly required.
