Already 4 months old when the scout caught it.
MCP Skills Extension
What it is
The Skills Extension (SEP-2640, also called "Skills over MCP") is a newly finalized official MCP extension that standardizes how an MCP server serves Agent Skills — directories of instructional files anchored by a SKILL.md — over the same connection that already serves its tools. It builds on MCP's existing Resources primitive rather than adding a fourth one: skills are exposed under a skill:// URI scheme, and a server declares two new methods, skills/list to enumerate what it offers and skills/get to fetch a specific skill by URI.
Why it's emerging now
Agent Skills — the SKILL.md convention for packaging reusable workflow instructions — spread fast through 2025–2026, but there was no standard way to distribute one from a remote server the way tools and resources already are; every integration improvised its own loading mechanism. A dedicated "Skills over MCP" working group spent mid-2026 narrowing the proposal — community votes cut a custom catalog format and archive-based distribution over complexity and script-execution concerns — before the spec reached Final status in September 2026. That lands right as the broader MCP ecosystem is converging on "extensions" (Apps, Tasks, now Skills) as the sanctioned way to grow the protocol without bloating its newly stateless core.
How it relates to what you know
It's the MCP-specific delivery mechanism for the already-known "Agent skills" concept, doing for skills what MCP Apps did for interactive UI and MCP Tasks did for long-running calls: turning an existing convention into a protocol-level primitive, governed by the same MCP extensions framework, instead of a vendor-specific loading scheme.