MCP authorization grew up: OAuth 2.1 is now part of the architecture_

MCP’s authorization specification requires OAuth 2.1 for HTTP transports. The important shift is from “can the agent connect?” to “which user, resource, and permission is this connection acting under?”

A connector that can read or write business systems is an identity boundary. Treating one shared token as infrastructure saves a week during a prototype and creates months of ambiguity later.

What changes in practice_

Map the resource owner, client, authorization server, token audience, scopes, and audit event before writing the happy-path tool call.

• Do not pass upstream tokens through unrelated services.
• Validate issuer and audience, not only signature.
• Keep user consent and revocation visible.

Our take_

The durable advantage is not adopting the newest tool first. It is building the identity, state, evidence, and operating boundaries that let a real team own the system after launch.