lint-clean-markdown

type	skill
lifecycle	stable
name	lint-clean-markdown
description	Write markdown that passes markdownlint on first attempt — encode the most common rules as muscle memory
tier	standard
inheritance	inheritable
applyTo	**/*.md
currency	"2026-05-01T00:00:00.000Z"
lastReviewed	"2026-05-01T00:00:00.000Z"

Lint-Clean Markdown

Eliminate the edit-lint-fix cycle by writing markdown correctly the first time.

When to Use

• Authoring any markdown file in this brain or in heir documentation
• Reviewing a PR that touches .md files
• The file just hit MD031, MD032, MD022, or MD060 errors

The Golden Rule

When in doubt: add a blank line.

Roughly 90% of markdown lint errors are missing blank lines. Lists, code blocks, and headings all need breathing room.

Core Rules Quick Reference

Rule	Code	Pattern	Mnemonic
Blank lines around lists	MD032	\n- item\n- item\n	"Lists breathe"
Blank lines around fences	MD031	\n\``code```\n`	"Code breathes"
Blank line before headings	MD022	text\n\n## Head	"Headers breathe"
Use dash for lists	MD004	- not * or +	"Dash dash dash"
No trailing whitespace	MD009	No spaces at line end	"Clean endings"
Hard line break in prose	(no MD code)	End line with \ then newline	"Backslash breaks"
Single final newline	MD047	One \n at EOF	"One newline"
Language on fences	MD040	```js not ```	"Name your code"
Consistent fence style	MD046	Use ``` not indent	"Fences only"
No bold as heading	MD036	Use ## not **text**	"Headers are headers"
Table separator spacing	MD060	Space around pipes	"Tables breathe too"

Rule Details

MD032: Blank Lines Around Lists

❌ Wrong: text immediately before/after list

✅ Correct: blank line before first - AND after last -

**Why**:

- Reason one
- Reason two

**Result**: Something

MD031: Blank Lines Around Code Blocks

❌ Wrong: text touching the fence markers

✅ Correct: blank line before opening ``` AND after closing ```

MD022: Blank Lines Before Headings

❌ Wrong: Some text.\n## Heading

✅ Correct: Some text.\n\n## Heading

Hard Line Breaks in Prose (the metadata-block trap)

The problem: Markdown collapses consecutive lines into one wrapped paragraph. A block of metadata like **Date**:, **Author**:, **Status**: on consecutive lines renders as one run-on sentence unless you force breaks.

The wrong fixes:

• Two trailing spaces (text ) — works in most renderers, but lints as MD009 (no trailing whitespace) and is invisible in source review.
• Empty lines between every item — turns the metadata block into a wall of paragraphs with massive vertical spacing.
• <br/> tag — works but mixes HTML into prose markdown; flagged as MD033 in many configs.

The right fix: end each line with a backslash (\) followed by a newline. This is the CommonMark hard-line-break form. Renders identically to two spaces, but is visible in source review and lints clean.

❌ Wrong (renders as one wrapped paragraph):

**Date**: 2026-05-01
**Author**: Supervisor
**Status**: Analysis

✅ Correct (renders as three lines):

**Date**: 2026-05-01 \
**Author**: Supervisor \
**Status**: Analysis

Note the spacing: one space before the backslash, then the newline. The last line in the block does not need the backslash (no break needed after the final line).

When this rule fires:

• Document metadata blocks (Date / Author / Status / Audience / Trigger) at the top of decision docs, ADRs, READMEs
• Address blocks, contact-info blocks
• Any list of consecutive **Label**: value lines that should visually be separate but should not have full paragraph spacing between them
• Poetry, lyrics, or any prose where line breaks are semantic

When this rule does NOT fire:

• Inside a real Markdown list (use - or 1. instead)
• Inside a table (use <br/> for in-cell line breaks)
• Inside a code fence (literal newlines work; no special handling needed)

MD004: Use Dash for Unordered Lists

❌ Wrong: * item or + item

✅ Correct: - item

MD040: Specify Language on Fenced Code

❌ Wrong: ``` (no language)

✅ Correct: ```javascript or ```text or ```markdown

Mermaid-Specific Rules

Template Blocks Use text

When showing a template/pattern (not a renderable diagram), use ```text instead of ```mermaid. The Mermaid parser will fail on placeholder text like [DIAGRAM_TYPE].

Diagram Type Required

Every ```mermaid block must declare its diagram type on the first line (flowchart TB, sequenceDiagram, etc.) — otherwise it renders blank.

Nested Code Block Problem

You cannot nest fenced code blocks in markdown. When documenting code-block rules:

1. Use inline code for short examples: `js`
2. Use descriptions instead of showing wrong examples literally
3. Use single examples showing only the correct form

This skill itself demonstrates the solution.

Pre-Write Mental Checklist

Before writing markdown, plan for:

1. ☐ Will I have lists? → blank lines around them
2. ☐ Will I have code blocks? → blank lines around them
3. ☐ Will I show "wrong" examples? → can't nest fences, describe instead
4. ☐ Will I have tables? → need | ---- | separator row
5. ☐ Will I have mermaid? → diagram type after init

Related

• markdown-mermaid — full markdown + Mermaid style guide
• markdown-mermaid § Mode Fragility — silent render failures

Falsifiability

• This skill has failed if markdown produced after activation still fails markdownlint with the same violation classes the skill explicitly addresses
• The rule set is stale if markdownlint releases new defaults this skill contradicts
• Wrong if the formatting constraints reduce readability rather than improve it (user consistently overrides the prescribed style)