Find the Exact Weight, Width, and Slant Ranges a Variable Font Ships

Your spec wanted 200-800. The report says wght 300-700. Redefine the extreme tokens to the real bounds so nothing silently clamps.

report: wght min 300, max 700
--font-weight-light: 300;   /* was 200 -> would clamp */
--font-weight-regular: 400;
--font-weight-bold: 700;    /* was 800 -> would clamp */

A width token only makes sense if the font ships a wdth axis. Check before designing the variant.

report: axes = [ wght 300-700 ]   (no wdth)
Decision: drop the planned --width-condensed token; this font has
no width axis. Either pick a font with wdth, or use a separate
condensed family.

If slnt exists, your oblique token uses degrees within the reported range. Negative leans forward.

report: slnt min -10, default 0, max 0
--style-oblique: "slnt" -10;  /* max forward lean this file allows */
/* equivalently font-style: oblique -10deg */

Named instances are the weights the foundry tuned. Aligning tokens to them keeps your scale on intentional design points.

named instances: Light(300) Regular(400) Medium(500) Bold(700)
--fw-light: 300; --fw-regular: 400; --fw-medium: 500; --fw-bold: 700;
/* 600 is reachable but not a named instance -> omit unless needed */

Export the JSON and commit it. When the font is updated, re-run and diff to catch range or instance changes that would break tokens.

tokens/font-axes.json  (from this tool)
  wght: 300..700, wdth: (none), opsz: 14..72
  instances: Light, Regular, Medium, Bold
CI: fail if any token weight falls outside wght min..max

A 200 weight token on a font whose wght min is 300 renders at 300 — no error, just a silently heavier caption. Always set token extremes to the reported min/max, never beyond.

If the report shows no wdth row, the font cannot do condensed or expanded widths; font-stretch will have no effect. Pick a font that ships a wdth axis, or use a separate condensed family. The mapper makes the absence obvious.

Without a slnt or ital axis, oblique/italic tokens won't work via variation settings. The browser may synthesise a fake oblique, but it will not match a designed italic. Confirm the axis exists before promising an italic token.

wdth is a percentage where 100 is normal. A range of 62.5-100 means the font condenses to 62.5% but does not expand past normal. Use those numbers directly in font-stretch (as a percent) or in font-variation-settings (as a number).

A static font has fixed weight and width with no ranges to read; the tool throws "This font has no variable axes (no fvar table or empty axis list)." For static fonts, use the Font Metrics Analyzer to read its fixed metrics instead.

Variable fonts are continuous, so a weight like 550 is valid even if there is no named instance at 550. Named instances are just the foundry's chosen presets. Use any in-range value; the named list is guidance, not a limit.

If wght default equals its min (e.g. default 400, min 400, max 900) the font ranges upward only. Your 'lighter than default' token is impossible. The default/min/max triple tells you which direction the axis can move.

Optical-size ranges are reported exactly from Fixed 16.16. A default at the small end means the font renders for small text unless you raise opsz or enable font-optical-sizing: auto. Map your context tokens within the reported range.

Fonts like Recursive or Roboto Flex ship custom axes (CASL, MONO, GRAD, parametric XOPQ/YOPQ). The report lists them with ranges. They have no CSS shorthand, so any token must use font-variation-settings with the explicit tag.