BodyReadability [check] v1.0.0

Verifies body prose meets readability requirements: 16px+ font-size, 1.5–1.7 line-height, letter-spacing within ±0.025em, and font-weight 400–500. Based on Butterick + Bringhurst typographic conventions.

signature: (html: string, css: string, context?: object) -> CheckResult predicate: // Body prose readability: // 1. font-size >= 16px on body (or root prose container) // 2. line-height between 1.5 and 1.7 (unitless) // 3. letter-spacing between -0.011em and 0.025em // 4. font-weight in [400, 500] for body (no thin 100-300 prose) proseSelectors = ['body', 'article', '.prose', '[role="article"]', 'main p'] for sel in proseSelectors: el = querySelector(sel) if !el: continue cs = getComputedStyle(el) fs = parseFloat(cs.fontSize) lh = parseFloat(cs.lineHeight) / fs // normalize to unitless ls = cs.letterSpacing === 'normal' ? 0 : parseFloat(cs.letterSpacing) / fs fw = parseInt(cs.fontWeight, 10)

if fs < 16: yield { selector: sel, fail: 'font-size-too-small', actual: fs, required: 16 } if lh < 1.5 || lh > 1.7: yield { selector: sel, fail: 'line-height-out-of-range', actual: round(lh, 2), required: '1.5-1.7' } if ls < -0.011 || ls > 0.025: yield { selector: sel, fail: 'letter-spacing-out-of-range', actual: ls, required: '-0.011em to 0.025em' } if fw < 400 || fw > 500: yield { selector: sel, fail: 'font-weight-not-body', actual: fw, required: '400-500' }

Validates

@community/rule-body-readability

Severity

medium

Failure Message Template

Prose '{selector}' fails readability: {fail}. Actual: {actual}, required: {required}. Adjust body CSS — typically font-size: 1rem; line-height: 1.6; letter-spacing: 0;.

Evaluation Method

automated

Tools

• playwright
• puppeteer
• @anthropic/claude-code

False Positive Rate

low

BodyReadability [check] v1.0.0

Verifies body prose meets readability requirements: 16px+ font-size, 1.5–1.7 line-height, letter-spacing within ±0.025em, and font-weight 400–500. Based on Butterick + Bringhurst typographic conventions.

signature: (html: string, css: string, context?: object) -> CheckResult predicate: // Body prose readability: // 1. font-size >= 16px on body (or root prose container) // 2. line-height between 1.5 and 1.7 (unitless) // 3. letter-spacing between -0.011em and 0.025em // 4. font-weight in [400, 500] for body (no thin 100-300 prose) proseSelectors = ['body', 'article', '.prose', '[role="article"]', 'main p'] for sel in proseSelectors: el = querySelector(sel) if !el: continue cs = getComputedStyle(el) fs = parseFloat(cs.fontSize) lh = parseFloat(cs.lineHeight) / fs // normalize to unitless ls = cs.letterSpacing === 'normal' ? 0 : parseFloat(cs.letterSpacing) / fs fw = parseInt(cs.fontWeight, 10)

if fs < 16: yield { selector: sel, fail: 'font-size-too-small', actual: fs, required: 16 } if lh < 1.5 || lh > 1.7: yield { selector: sel, fail: 'line-height-out-of-range', actual: round(lh, 2), required: '1.5-1.7' } if ls < -0.011 || ls > 0.025: yield { selector: sel, fail: 'letter-spacing-out-of-range', actual: ls, required: '-0.011em to 0.025em' } if fw < 400 || fw > 500: yield { selector: sel, fail: 'font-weight-not-body', actual: fw, required: '400-500' }

Validates

@community/rule-body-readability

Severity

medium

Failure Message Template

Prose '{selector}' fails readability: {fail}. Actual: {actual}, required: {required}. Adjust body CSS — typically font-size: 1rem; line-height: 1.6; letter-spacing: 0;.

Evaluation Method

automated

Tools

• playwright
• puppeteer
• @anthropic/claude-code

False Positive Rate

low

Validates

@community/rule-body-readability

Severity

medium

Failure Message Template

Prose '{selector}' fails readability: {fail}. Actual: {actual}, required: {required}. Adjust body CSS — typically font-size: 1rem; line-height: 1.6; letter-spacing: 0;.

Evaluation Method

automated

Tools

• playwright
• puppeteer
• @anthropic/claude-code

False Positive Rate

low