Resource indicators are a mechanism, standardized in RFC 8707, that lets a client specify exactly which protected resource it intends to use an access token for, so the authorization server can issue a token whose audience is locked to that one resource. This prevents a token issued for one API or MCP server from being replayed against a different one, which matters more once many distinct agents and resources are in play.
Frequently asked questions
Why does audience restriction matter more for agents than for typical web apps?
Agents commonly call multiple different tools and APIs in a single workflow, so without audience restriction a token stolen from one call could be replayed against a different, more sensitive resource.
Is RFC 8707 required for basic OAuth 2.0?
No, it's an extension; many simple OAuth deployments don't need it, but it becomes more important as the number of distinct protected resources grows.
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