markdown

name	markdown
description	Markdown linting and automated fixing using markdownlint-cli2. Use when Claude needs to: (1) Check markdown files for style issues, (2) Fix markdown formatting problems, (3) Ensure markdown follows best practices, (4) Validate markdown documents, or (5) Apply consistent markdown styling
license	MIT
metadata	{"author":"Ikuma Yamashita","version":"1.1"}

Markdown Lint

Automated markdown validation and fixing using markdownlint-cli2.

Workflow Overview

1. Run auto-fix     → markdownlint-cli2 --fix <file>
2. Check remaining  → markdownlint-cli2 <file>
3. Fix manually     → str_replace for structural issues
4. Verify           → markdownlint-cli2 <file> (should show 0 errors)

Expected results: Auto-fix resolves 70-90% of issues. Remaining 3-5 issues require manual correction.

Basic Commands

# Auto-fix single file
markdownlint-cli2 --fix document.md

# Check file
markdownlint-cli2 document.md

# Multiple files
markdownlint-cli2 --fix file1.md file2.md

# All markdown in directory
markdownlint-cli2 --fix "**/*.md"

# With custom config
markdownlint-cli2 --config .markdownlint.json document.md

File Paths

# Uploaded files
markdownlint-cli2 --fix /mnt/user-data/uploads/document.md

# Working directory
markdownlint-cli2 --fix /home/claude/document.md

# Output to user
cp /path/to/fixed.md /mnt/user-data/outputs/

Manual Fixes Required

Auto-fix cannot resolve these issues - they need Claude's judgment:

MD025 - Multiple H1 Headers

Why: Requires understanding document hierarchy
Fix: Convert extra H1s to appropriate level

# Main Title

# Second Title → Change to: ## Second Title

MD036 - Emphasis as Header

Why: Requires determining author intent
Fix: Replace bold/italic with proper header

**Section Title** → Change to: ## Section Title

MD013 - Line Too Long

Why: Requires deciding where to break content
Fix: Wrap at natural points (spaces, punctuation)

This is a very long line exceeding 80 characters that needs wrapping.
↓
This is a very long line exceeding 80 characters that needs
wrapping.

Exception: URLs typically exempt

MD041 - Missing First Line Header

Why: Requires structural decision
Fix: Add H1 at start or restructure

Execution Pattern

For Uploaded Files

# 1. Auto-fix
markdownlint-cli2 --fix /mnt/user-data/uploads/document.md

# 2. Check remaining
markdownlint-cli2 /mnt/user-data/uploads/document.md
# Output: "Summary: 3 error(s)"
# Lists specific errors like "MD025/single-title Multiple top-level headings"

# 3. Manual fixes (example)
str_replace "# Extra Title" → "## Extra Title"

# 4. Verify
markdownlint-cli2 /mnt/user-data/uploads/document.md
# Output: "Summary: 0 error(s)"

# 5. Output
cp /mnt/user-data/uploads/document.md /mnt/user-data/outputs/

For New Content

create_file /home/claude/doc.md "content..."
markdownlint-cli2 --fix /home/claude/doc.md
markdownlint-cli2 /home/claude/doc.md
# Fix remaining issues if any
cp /home/claude/doc.md /mnt/user-data/outputs/

Configuration

Create .markdownlint.json to customize rules:

{
  "default": true,
  "MD013": { "line_length": 120 },
  "MD033": false
}

Common adjustments:

• "MD013": false - Disable line length checking
• "MD013": { "line_length": 120 } - Increase limit to 120
• "MD013": { "code_blocks": false } - Exclude code blocks
• "MD033": false - Allow HTML
• "MD041": false - Don't require first line header

Config file search order:

1. .markdownlint-cli2.jsonc
2. .markdownlint-cli2.yaml
3. .markdownlint.jsonc / .markdownlint.json
4. .markdownlint.yaml / .markdownlint.yml

Reporting to User

Provide clear summary of fixes:

✅ Markdown linting complete!

Initial: 18 errors
After auto-fix: 4 errors
Manual fixes:
  • MD025: Converted 2 H1 headers to H2
  • MD036: Replaced bold with proper header
  • MD013: Wrapped long line

Final: 0 errors

Error Count Interpretation

Before auto-fix:

• 0-5: Minor issues
• 6-15: Moderate issues
• 16+: Significant issues

After auto-fix:

• 0-2: Excellent
• 3-5: Typical
• 6+: Check if config needed

Common Fix Patterns

# Multiple H1s - analyze structure first
# If sections: convert to H2
str_replace "# Introduction" → "## Introduction"

# If subsections: convert to H3
str_replace "# Details" → "### Details"

# Emphasis as headers - determine appropriate level
str_replace "**Important**" → "## Important"
str_replace "_Note_" → "### Note"

# Long lines - break at natural points
# After conjunctions: and, but, or
# After punctuation: , . ;
# Preserve URLs on single line

Troubleshooting

Auto-fix not working:

# Check file exists
view /path/to/file.md

# Verify permissions
ls -l /path/to/file.md

# Use absolute path
markdownlint-cli2 --fix /full/path/to/file.md

Too many errors after auto-fix:

# Create relaxed config
echo '{"MD013": false, "MD041": false}' > .markdownlint.json
markdownlint-cli2 --config .markdownlint.json --fix file.md

Specific rule causing issues:

• Disable in config: "MD013": false
• Or adjust parameters: "MD013": { "line_length": 120 }

When NOT to Lint

Skip linting when:

• Code examples intentionally violate rules
• Embedded HTML/JSX required (disable MD033)
• Generated docs with different conventions
• Legacy docs where changes break references

Use custom config to disable problematic rules.

Quick Rule Reference

Most common rules Claude will encounter:

• MD001 - Heading levels increment by one at a time
• MD003 - Consistent heading style (atx vs setext)
• MD004 - Consistent unordered list markers
• MD007 - Unordered list indentation (default: 2 spaces)
• MD009 - No trailing spaces
• MD010 - No hard tabs
• MD012 - No multiple consecutive blank lines
• MD013 - Line length (default: 80 chars)
• MD014 - No $ before shell commands unless showing output
• MD018 - Space after # in headings
• MD019 - No multiple spaces after # in headings
• MD022 - Blank lines around headings
• MD023 - Headings must start at beginning of line
• MD024 - No duplicate heading content
• MD025 - Single H1 only
• MD026 - No trailing punctuation in headings
• MD029 - Ordered list numbering style
• MD031 - Blank lines around fenced code blocks
• MD032 - Blank lines around lists
• MD033 - No inline HTML (unless explicitly allowed)
• MD034 - No bare URLs (wrap with <url> or [text](url))
• MD035 - Consistent horizontal rule style
• MD036 - No emphasis as headers
• MD037 - No spaces inside emphasis markers
• MD038 - No spaces inside code span backticks
• MD040 - Language for fenced code blocks
• MD041 - First line should be H1 header
• MD046 - Consistent code block style (fenced vs indented)
• MD047 - File must end with a single newline

Full rule documentation: https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md