Skill MCP server

skill-mcp

An MCP server that serves a directory of Agent Skills. Point it at skills; it lists them, hands out their instructions and their bundled files, and runs only the scripts a skill declares.

It is a generic adapter, not a curated set: the skills are content it reads, and the same build serves whatever it is pointed at.

npx @chrischall/skill-mcp                       # serves the example skill bundled here
SKILLS_DIR=~/my-skills npx @chrischall/skill-mcp

The npm package is @chrischall/skill-mcp (unscoped skill-mcp is taken by someone else on npm). Everything else — the repo, the binary, the registry identity io.github.chrischall/skill-mcp — is unscoped.

What a skill is

A directory holding SKILL.md: YAML frontmatter (name, description, and optionally the mcp-host: block below) followed by instructions, plus whatever files those instructions refer to. Three layouts are found under each root:

<root>/SKILL.md              # the root IS one skill
<root>/<name>/SKILL.md       # a directory of skills
<root>/skills/<name>/SKILL.md

A skill is served under its DIRECTORY name, never under the name in its own frontmatter (a frontmatter name that disagrees is reported and otherwise ignored; where the root itself is the skill, the root directory names it). That is a security rule, not a tidiness one: the owner's grant names a skill, so a bundle that could choose its own name could claim its neighbour's and be handed the neighbour's granted script and granted variables. For the same reason, two directories that really do contribute one name — only possible across two roots — have both refused and reported, rather than one of them winning by scan order.

The tools

skillfile takes one path. The design of record specifies a paths[] batch (8 paths per call, 1 MiB per entry, 4 MiB per call, one bad path failing only its own slot); shipping the singular form is a deliberate deferral, not an oversight, and those three bounds are what a later batching change has to honour. Read the caps as bounds on this server's own heap: they cap the allocation**, not only the answer, because a hosted child has a hard 256 MiB data limit and a bundle may be larger than that.

Each skill is also registered as an MCP prompt (its body is the message) and each bundled file as a resource (skill:///), because a client that supports those surfaces presents a skill better than a tool call does. It is a second door, never the only one: when this server runs on mcp-host and a registration narrows enabledTools, prompts/list and resources/list come back empty and the handshake stops advertising those capabilities — so the tools carry the whole experience.

Discovery reports, it never goes quiet

Shortened. The full README is on GitHub.