Enterprise-Managed Authorization for your MCP server: Setting Up and Testing XAA in Auth0

Summary

Connecting AI agents to enterprise APIs and MCP servers creates governance challenges when relying on traditional OAuth consent prompts. Cross App Access shifts authorization decisions to the enterprise identity provider, allowing IT administrators to manage agent permissions centrally. In this architecture, an identity provider like Okta authenticates the user and issues an Identity Assertion JWT Authorization Grant based on administrative policy. The requesting AI agent presents this assertion to Auth0, which validates the signature and exchanges it for a standard access token via a JWT-bearer grant. Protected APIs can then validate the final token normally without requiring code changes or direct user consent interactions.

Context

Enterprise organizations connecting AI agents like Claude or Cursor to internal MCP servers and APIs require centralized IT governance rather than having individual end users approve OAuth consent screens.

Approach / What changed

Auth0 implements the Cross App Access protocol to act as the Resource App authorization server. An enterprise IdP such as Okta acts as the policy enforcement point, evaluating admin rules and issuing an Identity Assertion JWT Authorization Grant (ID-JAG). The requesting client exchanges the ID-JAG with Auth0 using the JWT-bearer grant to obtain a standard access token for target API calls, optionally using a SAML interoperability layer when SAML authentication is used.

Takeaways

• Cross App Access shifts policy enforcement to an enterprise IdP, eliminating individual user consent screens for AI agent access to APIs and MCP servers.
• The flow relies on an Identity Assertion JWT Authorization Grant (ID-JAG), which contains claims such as issuer, audience, user identity, client ID, and scopes scoped down by IdP policies.
• Resource APIs do not require custom code changes to support XAA because Auth0 exchanges the ID-JAG for a standard Auth0 access token.

Related reading

• Auth0 · Aug 18, 2026

  Device Authorization Flow for a Rust CLI and an Axum API

  Command-line tools lack browser redirect capabilities, preventing standard OAuth login flows. To resolve this limitation, the OAuth 2.0 Device Authorization Flow issues a temporary device code, presents a verification URL to the user, and waits for authentication in an external browser. A Rust workspace demonstrates this end-to-end pattern across a CLI, an Axum web API, and a shared authentication library. The shared library relies on jsonwebtoken and reqwest to fetch JSON Web Key Sets and validate token signatures, issuers, and audiences against typed claims. Axum secures protected routes through custom FromRequestParts extractors that decode Bearer headers, enabling verified CLI access.

  Aniket Bhattacharyea

• Okta · Jul 17, 2026

  Enable Your SAML Requesting App for Cross App Access

  Cross App Access allows enterprise applications federated with Security Assertion Markup Language to interact with third-party resource APIs without migrating to OpenID Connect. The flow adapts the Identity Assertion Authorization Grant specification to SAML by adding three token exchange steps following the standard single sign-on handshake. First, the application exchanges the validated SAML assertion for an OAuth refresh token using Okta's token endpoint and a private key JSON Web Token. The application then uses the refresh token to request a short-lived Identity Assertion Authorization Grant token from Okta. Finally, the application presents the Identity Assertion Authorization Grant token to the third-party authorization server to obtain an OAuth access token.