Validation Rules Reference

Error Rules

Error rules result in a non-zero validation failure and prevent write operations when using agent-md write.

Rule ID	Severity	Configuration Key	Description
no-bold	Error	remove-bold (formatter)	Prohibits **bold** and __bold__ outside code blocks
heading-structure	Error	first-line-heading	Requires valid hierarchy: single H1, no skipped levels
table-syntax	Error	Built-in	Disallows alignment colons (:) in separator row `
simple-table-syntax	Error	Built-in	Tables must have ≤ 6 columns and consistent cell counts
table-trailing-spaces	Error	Built-in	Prohibits trailing whitespace inside table cells
no-ascii-graphs	Error	Built-in	Prohibits Unicode/ASCII box-drawing art diagrams
code-blocks	Error	blanks-around-fences	Requires valid language tags on fences and matching closing fences
list-formatting	Error	blanks-around-lists	Enforces uniform bullet symbols and proper list spacing
space-indentation	Error	Built-in	Forbids excessive indentation (>2 spaces) outside code
no-useless-links	Error	Built-in	Forbids [url](url) redundancy; requires <url> autolink
no-hard-tabs	Error	no-hard-tabs	Forbids \t tab characters outside code blocks

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Warning Rules

Warning rules report style inconsistencies without failing the valid status.

Rule ID	Severity	Configuration Key	Description
no-duplicate-headings	Warning	no-duplicate-headings	Flags duplicate heading titles within a single file
no-multiple-blanks	Warning	compact-blank-lines	Flags consecutive blank lines
line-length	Warning	line-length / max-line-length	Flags lines exceeding maximum character threshold

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Configuration Mapping

Rules can be toggled in .agent-md.json or .markdownlint.json:

{
  "blanks-around-headings": true,
  "blanks-around-lists": true,
  "blanks-around-fences": true,
  "first-line-heading": false,
  "no-duplicate-headings": true,
  "no-hard-tabs": true,
  "line-length": false,
  "max-line-length": 0
}