MCP Authorization Explained

Authorization determines what an authenticated caller is allowed to do. For HTTP-based MCP, the specification defines an OAuth-oriented authorization model where the MCP server acts as a protected resource.

Validate token audience

A server must ensure the presented token was issued for that server/resource. Accepting a token intended for another API breaks a critical security boundary.

Use correct errors

Invalid or expired credentials typically map to 401. Valid identity with insufficient permission maps to 403. Keep error details useful without disclosing sensitive policy internals.

Authorization remains tool-specific

A valid connection does not imply permission for every tool. Check scopes, roles, ownership, and tenant constraints inside the relevant capability boundary.