One token, two jobs: ID-JAG in enterprise access and agent registration

ID-JAG, or Identity Assertion JWT Authorization Grant, is a proposed IETF OAuth mechanism for exchanging a short-lived, audience-specific signed assertion for another credential, rather than serving as an API access token itself. The same JWT type supports two distinct use cases: enterprise-managed authorization, where a company’s identity provider authorizes an AI client to access an MCP server under centrally managed SSO policy, and agent-verified registration, where an agent provider attests to a user’s identity so a service can provision or bind an account. Enterprise authorization relies on an existing mutual SSO trust relationship and redeems the ID-JAG directly for an access token, while registration relies on a curated provider trust list, verified contact information, recent authentication, and an intermediate service-signed assertion before token issuance. Their claims, validation requirements, provisioning models, and revocation mechanisms therefore differ despite sharing a token format. Organizations may need both integrations, while agent registration also has limitations when providers do not issue ID-JAGs, requiring alternatives such as user-confirmed flows; an unresolved issue remains around agents operating across both provider-based registration and enterprise policy environments.

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