Roots, Sampling, and Logging are deprecated — new capabilities now ship as opt-in extensions

Model Context Protocol Blog·medium signal

The RC deprecates three original-spec features (Roots, Sampling, Logging) under the protocol's first formal deprecation policy, and introduces an extensions framework where new capabilities ship opt-in and stabilize outside the spec before ever moving into it. For server authors this changes the upgrade calculus: you can adopt an extension without waiting for a spec revision, and you now get a defined window before a feature you depend on disappears. Audit any server still calling Sampling or Roots before the final spec lands on July 28, 2026.