API & MCP

Everything a person can do on Webfont Subsetter (WOFF & TTF), a program or AI agent can do with the same inputs and get the identical result.

HTTP API

POST https://luminafontsubset.usefulweb.app/api/v1/calculate – run Webfont Subsetter (WOFF & TTF)
GET https://luminafontsubset.usefulweb.app/api/v1/tool – inputs, output schema, examples
OpenAPI 3.1: /openapi.json · /openapi.yaml
Errors: application/problem+json; 422 includes per-field errors.

Webfont Subsetter (WOFF & TTF)

Upload a TrueType font (TTF or WOFF) and keep only the characters you need: type them, paste a page's text, add Unicode ranges or tick common blocks. Variable fonts can be frozen at one weight. You get a WOFF 1.0 or TTF file with kerning kept as a kern table, the size saving and a ready @font-face rule with unicode-range.

Inputs of Webfont Subsetter (WOFF & TTF)
Field	Type	Default	Description
`font` (required)	file	—	Font (TTF or WOFF with TrueType outlines; up to 10 MB; uploaded to the server)
`text`	textarea	—	Characters or text to keep
`ranges`	text	—	Unicode ranges (e.g. U+0020-007E, U+00E9)
`presets`	multiselect (basic-latin, latin-1, latin-ext-a, punctuation, greek, cyrillic, digits)	[]	Common character blocks
`format`	select (woff, ttf)	"woff"	Output format
`kerning`	boolean	true	Keep kerning (as a kern table)
`axes`	text	—	Freeze a variable font at (e.g. wght=700; empty = keep the default instance)

Every result contains

inputs (normalised, defaults applied), summary, result (validated against the published schema), units, assumptions, sources, warnings, computedAt and links.

MCP (Model Context Protocol)

Streamable HTTP endpoint: https://luminafontsubset.usefulweb.app/mcp – protocol revisions 2026-07-28 (stateless) and 2025-11-25 / 2025-06-18 / 2025-03-26 (initialize handshake).
Tools: lumina_font_subset
Local stdio connector: node src/mcp-stdio.ts --tool=lumina-font-subset

{
  "mcpServers": {
    "lumina-font-subset": { "type": "http", "url": "https://luminafontsubset.usefulweb.app/mcp" }
  }
}