SEP-2640 merges as Final: Agent Skills get a spec-level home over MCP Resources, the first proposal accepted since the 2026-07-28 release

The MCP maintainers merged SEP-2640, the Skills Extension, on 2026-09-13 with status Final. It is an Extensions Track proposal, authored by Peter Alexander, Ola Hungerford, Sambhav Kothari and Aditya Kumar on behalf of the Skills Over MCP Working Group, and it had been open since 2026-04-23. A companion pull request adding an overview page under modelcontextprotocol.io/extensions/skills merged forty-two seconds later.

The proposal does not invent a new primitive. In its own words, it "defines a convention for serving Agent Skills over MCP using the existing Resources primitive." A skill is a directory of files, at minimum a SKILL.md, and each file becomes an MCP resource, conventionally under a skill:// URI whose final path segment must equal the skill's declared name. Two methods are required of any server that declares the extension: skills/list, which enumerates the skills a server serves and may return a partial listing for large or generated catalogs, and skills/get, which returns one skill's entry by URI, including skills absent from the listing. A third, resources/directory/read, is optional and lists the direct children of a directory resource. The skill format itself, the frontmatter, naming rules and progressive-disclosure model, is delegated to the separate Agent Skills specification at agentskills.io; the SEP covers only the transport binding. The extension identifier is io.modelcontextprotocol/skills, and on the 2026-07-28 revision and later, skills/list results carry the base protocol's list-caching attributes from SEP-2549.

The merge has a place in the calendar as well as the protocol. A search of the specification repository for merged SEP-labelled pull requests since the 2026-07-28 release returns exactly one result, this one. The pipeline had produced no accepted proposals in the seven weeks after the release, and the roadmap published 2026-08-22 reset review priorities around five areas. Because SEP-2640 is an extension rather than a change to the core revision, the draft changelog for the next dated release still reads "Changes since the most recent release will accumulate here." Two of the pipeline's oldest open proposals, SEP-1803 on event subscriptions and SEP-1862 on tool resolution, were closed unmerged on 2026-09-02, leaving 42 SEP pull requests open on 2026-09-15.

Reference support arrived ahead of the merge. MCP Inspector 2.6.0, published 2026-09-09, lists "support the Skills extension (SEP-2640) with digest verification" among its changes, alongside a follow-up that measures a skill reached from another skill.