markdown-formatting by denolfe

---
name: markdown-formatting
description: Format and lint markdown and MDX files using markdownlint with comprehensive rule knowledge for automated and manual fixes. Use when working with .md or .mdx files, formatting documentation, linting markdown/MDX, or when user mentions markdown issues, formatting problems, or documentation standards.
allowed-tools:
  - Read
  - Edit
  - Bash
  - Grep
  - Glob
---

# Markdown & MDX Formatting & Linting

Format and lint markdown and MDX files using markdownlint CLI tools with comprehensive understanding of all markdown rules.

## Quick Start

```bash
# Check if markdownlint is available
which markdownlint || which markdownlint

# Install if needed
pnpm add -D markdownlint
# or
npm install -g markdownlint

# Auto-fix files (markdown and MDX)
markdownlint --fix "**/*.{md,mdx}"

# Check specific files
markdownlint README.md docs/**/*.md content/**/*.mdx
```

## Configuration Detection

Check for config files in this order:

1. `.markdownlint.json`
2. `.markdownlint.jsonc`
3. `.markdownlint.yaml`
4. `.markdownlintrc`
5. `markdownlint` key in `package.json`

## Common Workflow

1. **Detect environment**: Check for markdownlint CLI
2. **Find config**: Look for config files
3. **Run linter**: Identify issues
4. **Apply fixes**: Auto-fix or manual
5. **Verify**: Re-run to confirm

## Most Common Issues & Quick Fixes

### Headings

- **MD001**: Heading levels increment (# → ## → ### not # → ###)
- **MD018/MD019**: Single space after hash (`# Heading` not `#Heading`)
- **MD022**: Blank lines around headings
- **MD025**: Single H1 per document
- **MD041**: First line should be H1

```markdown
<!-- Good heading structure -->
# Main Title

## Section

### Subsection

Content here...
```

### Lists

- **MD004**: Consistent list markers (all `-` or all `*`)
- **MD007**: Nested lists indent 2 spaces
- **MD030**: Single space after list marker
- **MD032**: Blank lines around lists

```markdown
<!-- Good list structure -->
- Item 1
  - Nested item
  - Another nested
- Item 2
```

### Whitespace

- **MD009**: No trailing spaces
- **MD010**: Use spaces not tabs
- **MD012**: Single blank lines (not multiple)
- **MD047**: File ends with newline

### Links & Images

- **MD034**: Wrap bare URLs in `<>`: `<http://example.com>`
- **MD042**: Links need text: `[Link Text](url)` not `[](url)`
- **MD045**: Images need alt text: `![Description](image.png)`

### Code Blocks

- **MD031**: Blank lines around code blocks
- **MD040**: Specify language for code blocks

````markdown
<!-- Good code block -->
Text before

```javascript
const code = 'here';
```

Text after
````

## CLI Commands

```bash
# Fix all markdown and MDX files
markdownlint --fix "**/*.{md,mdx}"

# Fix specific files
markdownlint --fix README.md CHANGELOG.md content/blog.mdx

# Check without fixing
markdownlint "**/*.{md,mdx}"

# Use specific config
markdownlint --config .markdownlint.json "**/*.{md,mdx}"

# Ignore specific rules
markdownlint --disable MD013 MD033 "**/*.{md,mdx}"

# Output JSON for parsing
markdownlint --json "**/*.{md,mdx}"
```

## Common Patterns

### Fix Multiple Issues at Once

```markdown
<!-- Before -->
#Title
Some text with trailing spaces
 Tab indented line

- Item 1
* Item 2
Visit http://example.com

<!-- After -->
# Title

Some text with trailing spaces
    Space indented line

- Item 1
- Item 2

Visit <http://example.com>
```

### Add to package.json

```json
{
  "scripts": {
    "lint:md": "markdownlint \"**/*.{md,mdx}\" --ignore node_modules",
    "lint:md:fix": "markdownlint \"**/*.{md,mdx}\" --ignore node_modules --fix"
  }
}
```

## Detailed Rules Reference

For comprehensive documentation of all markdown rules with examples and fixes, see [rules-reference.md](./rules-reference.md).

## Resources

- [markdownlint GitHub](https://github.com/DavidAnson/markdownlint)
- [markdownlint Rules](https://github.com/DavidAnson/markdownlint/blob/main/doc/Rules.md)