- [Microsoft Entra ID Auth SDK (sidecar) documentation](/entra/msidweb/agent-id-sdk/overview)
Traditional service principals were designed for static, deterministic workloads. Microsoft Entra Agent ID exists because service principals lack the governance infrastructure AI agents need. There's no enforced sponsorship, no agent-aware audit entries, and no blueprint-managed lifecycle. For more information, see [Agent identities, service principals, and applications](agent-service-principals.md).
To call an API from an agent, you need to obtain an access token that the agent can use to authenticate itself to the API. We recommend using the *Microsoft.Identity.Web* SDK for .NET to call your web APIs. This SDK simplifies the process of acquiring and validating tokens. For other languages, use the [Microsoft Entra ID Auth SDK (sidecar)](/entra/msidweb/agent-id-sdk/overview).
- [Call API: Azure services](../agent-id/call-api-azure-services.md) (New)