Markdown Accessibility Skill

Reusable knowledge module for the markdown-a11y-assistant, markdown-scanner, and markdown-fixer agents and the markdown-accessibility always-on instructions. Provides pattern libraries, severity scoring, fix templates, emoji translation maps, diagram description templates, and GitHub anchor generation rules for comprehensive markdown accessibility auditing across 9 domains.

Domains Covered

1. Descriptive Links (WCAG 2.4.4) - Ambiguous link text, bare URLs, repeated identical text
2. Image Alt Text (WCAG 1.1.1) - Missing, empty, filename-as-alt, generic placeholders
3. Heading Hierarchy (WCAG 1.3.1 / 2.4.6) - Skipped levels, multiple H1s, bold-as-heading
4. Table Accessibility (WCAG 1.3.1) - Missing descriptions, empty headers, layout tables
5. Emoji (WCAG 1.3.3 / Cognitive) - Remove-all, remove-decorative, translate, or leave-unchanged modes
6. Mermaid and ASCII Diagrams (WCAG 1.1.1 / 1.3.1) - Replace with accessible text + collapsible source
7. Em-Dash / En-Dash Normalization (Cognitive) - Normalize to - or leave unchanged
8. Anchor Link Validation (WCAG 2.4.4) - Validate #anchor links against actual headings
9. Plain Language and List Structure (Cognitive) - Emoji bullets, passive voice, sentence length

Severity Scoring

Issue	Severity	WCAG	Auto-fix?
Image missing alt text	Critical	1.1.1 (A)	No - needs visual judgment
Mermaid diagram with no text alternative	Critical	1.1.1 (A)	Partial - simple diagrams auto-described; complex need human
ASCII diagram with no text description	Critical	1.1.1 (A)	Partial - flag and wrap; description needs human or auto-gen
Broken anchor link	Serious	2.4.4 (A)	No - confirm which end changes
Ambiguous link text ("here", "click here")	Serious	2.4.4 (A)	Yes - rewrite using surrounding context
Skipped heading level	Serious	1.3.1 (A)	Yes - interpolate missing level
Multiple H1s	Serious	1.3.1 (A)	Yes - demote all but first
Emoji in heading	Moderate	Cognitive	Yes - remove or translate per preference
Consecutive emoji (2+)	Moderate	1.3.3 (A)	Yes - remove sequence or translate
Emoji used as bullet	Moderate	1.3.1 (A)	Yes - replace with -
Em-dash in prose	Moderate	Cognitive	Yes - replace with -
Table without preceding description	Moderate	1.3.1 (A)	Yes - add one-sentence summary
Bold text used as heading	Minor	2.4.6 (AA)	Yes - convert to appropriate heading
Bare URL in prose	Minor	2.4.4 (A)	Yes - wrap with descriptive text
Emoji used for meaning, single inline	Minor	1.3.3 (A)	Conditional - remove-all: yes; remove-decorative: flag; translate: translate

Scoring Formula

File Score = 100 - (sum of weighted findings)

Critical: -15 pts each
Serious:  - 7 pts each
Moderate: - 3 pts each
Minor:    - 1 pt each

Floor: 0

Score Grades

Score	Grade	Meaning
90-100	A	Excellent - accessible documentation
75-89	B	Good - minor issues
50-74	C	Needs Work - several barriers
25-49	D	Poor - significant barriers
0-24	F	Failing - critical AT barriers

Emoji Handling Modes

The agent supports four modes. The active mode is determined by the nearest markdown-accessibility.instructions.md file in scope. If no instructions file sets a mode, the default is remove-decorative.

This repository: The .github/instructions/markdown-accessibility.instructions.md file in this repo sets mode to remove-all. All emoji are removed, not translated. This overrides the skill default.

Mode	Description	Default?
remove-all	Strip every emoji from prose, headings, and bullets. Keep surrounding plain-text meaning.	No (repo override sets this)
remove-decorative	Remove emoji in headings, bullets, and consecutive sequences; flag single inline for review	Skill default (no override)
translate	Replace known emoji with (English) text; flag unknown for review	No
leave-unchanged	Do not flag or modify any emoji	No

Mode resolution order:

1. Agent system prompt or per-task explicit mode override
2. Nearest *.instructions.md file in scope (e.g., .github/instructions/markdown-accessibility.instructions.md)
3. Skill default (remove-decorative)

Emoji Translation Map

When using translate mode, replace each emoji with the parenthesized English equivalent:

Emoji	Translation	Emoji	Translation
🚀	(Launch)	✅	(Done)
⚠️	(Warning)	❌	(Error)
📝	(Note)	💡	(Tip)
🔧	(Configuration)	📚	(Documentation)
🎯	(Goal)	✨	(New)
🔍	(Search)	🛠️	(Tools)
👋	(Hello)	🎉	(Celebration)
⭐	(Featured)	💬	(Discussion)
🏠	(Home)	📊	(Data)
🔒	(Security)	🌐	(Web)
📦	(Package)	🔗	(Link)
📋	(Checklist)	🏆	(Achievement)
⚡	(Quick)	👍	(Approved)
👎	(Rejected)	🐛	(Bug)
🤝	(Collaboration)	🎓	(Learning)
🔑	(Key)	📌	(Pinned)
ℹ️	(Info)	🔄	(Refresh)
➕	(Add)	➖	(Remove)
💻	(Code)	🔔	(Notification)
📣	(Announcement)	🧪	(Test)
🎨	(Design)	🌟	(Highlight)
📈	(Increase)	📉	(Decrease)
🏗️	(Build)	🔐	(Locked)
📂	(Folder)	📁	(Folder)
🗂️	(Category)	🗃️	(Archive)
⚙️	(Settings)	🏁	(Finish)
🚧	(In Progress)	🚫	(Not Allowed)
✔️	(Check)	➡️	(Next)
⬆️	(Up)	⬇️	(Down)

For emoji not in this table: flag as needs-human-review. Do not guess.

Emoji Detection Unicode Ranges

[\u{1F600}-\u{1F64F}]  - Emoticons
[\u{1F300}-\u{1F5FF}]  - Misc symbols and pictographs
[\u{1F680}-\u{1F6FF}]  - Transport and map symbols
[\u{1F700}-\u{1F77F}]  - Alchemical symbols
[\u{1F780}-\u{1F7FF}]  - Geometric shapes extended
[\u{1F900}-\u{1F9FF}]  - Supplemental symbols
[\u{1FA70}-\u{1FAFF}]  - Symbols and pictographs extended
[\u{2600}-\u{26FF}]    - Misc symbols
[\u{2700}-\u{27BF}]    - Dingbats
[\u{1F1E0}-\u{1F1FF}]  - Flags
[\u{FE00}-\u{FE0F}]    - Variation selectors

Emoji-as-bullet pattern: list item where the first non-whitespace character is an emoji.

Pattern Library: Mermaid and ASCII Diagrams

Mermaid Detection

Lines matching ```mermaid (with optional leading spaces/tabs).

Mermaid Description Templates

Type	Description Template
graph TD/LR/RL/BT / flowchart	"The following [direction] diagram shows: [list major nodes and connections from source]"
sequenceDiagram	"The following sequence diagram shows the interaction between [participants]: [list each message in order]"
classDiagram	"The following class diagram shows [N] classes: [list class names, key properties, and relationships]"
erDiagram	"The following entity-relationship diagram shows [entities] with these relationships: [list relationships]"
gantt	"The following Gantt chart shows project tasks: [list section names and tasks with dates if available]"
pie	"The following pie chart shows [title] with values: [list each label and percentage/value if available]"
stateDiagram	"The following state diagram shows [N] states: [list state names and transition triggers]"
mindmap	"The following mind map shows [root topic] with branches: [list top-level branch names]"
timeline	"The following timeline shows events: [list events in chronological order]"

Auto-generate description for: graph, flowchart, pie, gantt, mindmap, timeline. Flag for human review: sequenceDiagram, classDiagram, erDiagram, stateDiagram (complex enough to need human verification).

Mermaid Replacement Template

[Generated or user-provided text description - this is the primary accessible content]

<details>
<summary>Diagram source (Mermaid)</summary>

```mermaid
[original diagram source - unchanged]
```text

</details>

ASCII Diagram Detection

ASCII art patterns: non-code-block lines (or unnamed code blocks) containing combinations of +, -, |, /, \, >, <, ^, v, * forming a visual structure. Minimum 3 lines with consistent column alignment.

ASCII Diagram Replacement Template

[Generated or user-provided text description - this is the primary accessible content]

<details>
<summary>ASCII diagram</summary>

[original ASCII art - unchanged]

</details>

Pattern Library: Ambiguous Link Detection

Match these patterns (case-insensitive, trim whitespace):

Exact-match violations

here, click here, read more, learn more, more, more info,
link, details, info, go, see more, continue, start, download,
view, open, submit, this, that

Starts-with violations

click here to ..., read more about ..., learn more about ...,
here to ..., see more ...

URL-as-text pattern

Any link where visible text matches https?:// or www\.

Repeated identical text

Multiple [X](url1) and [X](url2) with same X but different URLs on the same page.

Safe patterns (do not flag)

• Badge links: [![text](img)](url) at top of README
• Section self-references: [Installation](#installation) where text matches heading
• Footer resource lists using the resource/tool name as text

Pattern Library: GitHub Anchor Generation

GitHub converts headings to anchor IDs using these rules:

1. Lowercase entire string
2. Remove all characters except: letters (a-z), digits (0-9), spaces, hyphens
3. Replace spaces with hyphens
4. Remove leading and trailing hyphens

Examples

Heading	Anchor
# Getting Started	#getting-started
## API: v2.0 Reference	#api-v20-reference
### What's New?	#whats-new
## C# and .NET Support	#c-and-net-support
## Step 1: Installation	#step-1-installation
## FAQ (Frequently Asked Questions)	#faq-frequently-asked-questions
## 🚀 Quick Start	#-quick-start (emoji becomes empty, may vary)

For headings containing emoji: GitHub strips the emoji character and generates an anchor from the remaining text. Anchors referencing emoji-containing headings are fragile and should be flagged.

Pattern Library: Emoji Detection

Unicode emoji ranges for regex detection:

[\u{1F600}-\u{1F64F}]  # Emoticons
[\u{1F300}-\u{1F5FF}]  # Misc symbols and pictographs
[\u{1F680}-\u{1F6FF}]  # Transport and map symbols
[\u{1F700}-\u{1F77F}]  # Alchemical symbols
[\u{1F780}-\u{1F7FF}]  # Geometric shapes extended
[\u{1F800}-\u{1F8FF}]  # Supplemental arrows-C
[\u{1F900}-\u{1F9FF}]  # Supplemental symbols and pictographs
[\u{1FA00}-\u{1FA6F}]  # Chess symbols
[\u{1FA70}-\u{1FAFF}]  # Symbols and pictographs extended-A
[\u{2600}-\u{26FF}]    # Misc symbols
[\u{2700}-\u{27BF}]    # Dingbats
[\u{FE00}-\u{FE0F}]    # Variation selectors
[\u{1F1E0}-\u{1F1FF}]  # Flags

Emoji-as-bullet pattern: List item where first non-whitespace character is an emoji.

Pattern Library: Em-Dash and En-Dash

Detection patterns:

—           Unicode em-dash (U+2014)
–           Unicode en-dash (U+2013)
---         Three hyphens in prose (not on its own line as HR)
--          Two hyphens in prose (used as em-dash substitute)

Safe to skip (do not modify):

• Line containing only --- (horizontal rule)
• Content inside ``` code fences
• Content inside backtick inline code
• YAML front matter block
• HTML comment blocks <!-- -->

Replacement: - (space + hyphen + space)

En-dash in numeric ranges: 2–4 hours -> 2 - 4 hours

Pattern Library: Mermaid Diagrams

Detection: Lines matching ```mermaid (with optional leading spaces/tabs)

Diagram types and description guidance:

Type	Description Template
graph TD/LR/RL/BT	"The following diagram shows a [direction] flowchart: [list major nodes and connections]"
sequenceDiagram	"The following sequence diagram shows the interaction between [participants]: [list message exchanges]"
classDiagram	"The following class diagram shows [N] classes: [list class names and key relationships]"
erDiagram	"The following entity-relationship diagram shows [entities] and their relationships: [list relationships]"
gantt	"The following Gantt chart shows project phases: [list tasks and timeframes]"
pie	"The following pie chart shows [title] with values: [list segment names and values if available]"
stateDiagram	"The following state diagram shows [N] states and transitions: [list states and transition triggers]"

Wrapping template:

[Generated or user-provided text description]

<details>
<summary>Diagram source (Mermaid)</summary>

```mermaid
[original diagram source]
```text

</details>

Fix Templates

Ambiguous link fix

# Before
For more information, see [here](https://example.com/guide).

# After
For more information, see the [installation guide](https://example.com/guide).

Emoji bullet fix

# Before
- 🚀 Deploy to production
- ✅ Run tests

# After
- Deploy to production
- Run tests

Emoji heading fix

# Before
## 🔧 Configuration

# After
## Configuration

Em-dash fix

# Before
The agent—when invoked—will scan all files.

# After
The agent - when invoked - will scan all files.

Table description fix

# Before
| Rule | Severity | Auto-fix |
|------|----------|----------|

# After
The following table lists rules with their severity level and whether they can be fixed automatically.

| Rule | Severity | Auto-fix |
|------|----------|----------|

Broken anchor fix

# Before (broken)
See [Installation](#instalation) for setup steps.

# Heading in file
## Installation

# After (corrected)
See [Installation](#installation) for setup steps.

Markdownlint Rules Reference

Rule	Name	Accessibility Relevance
MD001	heading-increment	Heading hierarchy (WCAG 1.3.1)
MD022	blanks-around-headings	Parsing reliability
MD024	no-duplicate-heading	Unique section identity (WCAG 2.4.6)
MD025	single-title / single-h1	One H1 per document
MD033	no-inline-html	May hide structure from parsers
MD034	no-bare-urls	Ambiguous links (WCAG 2.4.4)
MD041	first-line-heading	Document structure
MD055	table-pipe-style	Table parsing consistency
MD056	table-column-count	Table structural integrity

Command: npx --yes markdownlint-cli2 <filepath>