The MCP server

The skill tells a model to verify a font carries a feature before using it. @sceboucher/hypertype lets it actually check. It is a local MCP server (runs over stdio via npx, no API key, no hosting) that reads the OpenType features and variable axes straight from the served font file. So font-variant-caps: small-caps on a font with no small caps comes back as a real warning instead of a silent fake.

It does three jobs: verify what a font can do, generate a type system that’s guaranteed renderable, and critique the hierarchy of CSS you already have. Running locally is also the only way to analyze your installed and Adobe-activated fonts (they live in the OS font directory, where a hosted server can’t see them).

Install

npx -y @sceboucher/hypertype install

Or point any AI assistant at the install runbook. In Claude Code: claude mcp add hypertype -- npx -y @sceboucher/hypertype.

The ten tools

Verify

Tool	What it does
analyze_font	Report the OpenType features and variable axes a font actually ships, read from the served file. Accepts a Google family name, a font URL, or an installed family name. Catches the Google reduced-subset gotcha.
check_css	The no-op catcher. Check every font-variant-* / font-feature-settings declaration against the font’s real features and report whether each resolves, is a silent no-op, or is degraded (the browser synthesizes a faked small-caps).
slab_readiness	Whether a font ships a width axis, so slab.js can do the authentic same-cap-height justified slab instead of scaling font size per line.
font_license	OFL / Apache (self-hostable) vs Adobe (CDN-only) vs verify. The “safe to ship in a repo?” check.

Generate

Tool	What it does
recommend_css	Turn a plain-language intent (“tabular figures and a slashed zero”) into correct font-variant-* CSS, verified against the font. Features it lacks are reported, not emitted as CSS that silently fails.
design_type_system	Emit a context-fit type system: a scale ratio chosen for the surface, role tokens (size, line-height, weight, tracking), rem-safe fluid clamp(), the OpenType features that context calls for, and ready CSS. Proposed fonts are verified, so the system is guaranteed renderable.
pair_fonts	Suggest a display + text pairing where both fonts carry the features you need, drawn from a de-AI’d shortlist and verified against the served files.

Critique and discover

Tool	What it does
critique_hierarchy	Analyze CSS or an HTML document and flag the known hierarchy tells (flat hierarchy, bold-only hierarchy, sub-1.2x size steps, symmetric heading margins, too many styles, one global line-height, runaway measure). Each finding includes a fix.
list_sources	Which font sources this machine can reach: Google and URLs always; Adobe and installed fonts only because the server runs locally.
find_fonts	Find fonts that carry a set of OpenType features (and optional axes) across the sources you have, from a prebuilt verified index. “Which fonts ship real small caps and a slashed zero?”

How it works

The server reads the OpenType FeatureList (GSUB/GPOS) and fvar axes straight from the sfnt bytes, decompressing woff2 first. That is deliberate: the high-level font libraries under-report features on Google’s woff2, and the Google CSS API serves a reduced subset (for example, Source Serif 4 ships neither small caps nor a slashed zero in Google’s file). Analyzing the file the browser actually loads is the only honest answer.

The judgment behind design_type_system and critique_hierarchy is written up in two guides: building a type system and using hierarchy well.

Full tool schemas and config are in the package README.