Frontmatter field reference

Complete reference for YAML frontmatter fields in VectorLint rule files.

Every VectorLint rule file begins with a YAML frontmatter block that controls how VectorLint runs the evaluation, handles the result, and reports violations. The Markdown body that follows is the prompt sent to the LLM.

---
id: MyRule
name: My Rule
type: check
severity: error
---

Your LLM prompt goes here.

Required fields

Field	Type	Description
id	string	Unique identifier for the rule. Used in CLI output and in .vectorlint.ini overrides. PascalCase recommended (e.g., GrammarChecker).
name	string	Human-readable display name shown in CLI output.

Optional fields

Field	Default	Description
specVersion	(none)	Rule spec version. Set to 1.0.0 for rules using the full judge schema.
evaluator	base	Evaluator type. Use base for standard rules. Use technical-accuracy for rules that verify factual claims against live web search (requires a search provider).
type	check	Evaluation mode. check finds specific, countable violations. judge scores content against weighted criteria on a 1–4 rubric.
severity	warning	How a failing result is reported. error causes a non-zero exit code; warning reports the issue without failing the run.
evaluateAs	chunk	Whether to evaluate content in sections (chunk) or as a single unit (document). Chunking is applied automatically to documents over 600 words. Set to document to disable chunking for a specific rule.
target	(none)	Regex specification to extract and evaluate a specific portion of the content, such as the H1 headline. See Target fields below.
criteria	(none)	Required when type is judge. Defines the scoring dimensions and their weights. See Criteria fields below.

Target fields

The target field narrows evaluation to a specific part of the document. It is an object with the following sub-fields:

Field	Type	Required	Description
regex	string	Yes	Regular expression pattern to match the target content.
flags	string	No	Regex flags (e.g., "mu" for multiline and Unicode).
group	number	No	Capture group index to extract. If omitted, the full match is used.
required	boolean	No	When true, a missing match immediately reports an error with the suggestion text and skips LLM evaluation. When false or omitted, a missing match causes VectorLint to evaluate the full document instead.
suggestion	string	No	Message shown when required: true and the pattern does not match.

Example — targeting only the H1 headline:

target:
  regex: '^#\s+(.+)$'
  flags: "mu"
  group: 1
  required: true
  suggestion: Add an H1 headline for the article.

Criteria fields

The criteria field is an array of criterion objects used with type: judge. Each criterion defines one scoring dimension.

Field	Type	Required	Description
name	string	Yes	Human-readable criterion name shown in CLI output.
id	string	Yes	Unique identifier for this criterion. PascalCase recommended (e.g., TechnicalAccuracy). Referenced in the Markdown body rubric as # CriterionName <weight=N>.
weight	number	No	Relative importance of this criterion in the weighted average. Higher values increase the criterion’s influence on the final score. Defaults to 1.
target	object	No	Criterion-specific content matching. Uses the same sub-fields as the top-level target. Overrides the rule-level target for this criterion only.

Example — judge rule with two weighted criteria:

criteria:
  - name: Technical Accuracy
    id: TechnicalAccuracy
    weight: 40
  - name: Readability
    id: Readability
    weight: 30

Complete example

The following rule uses all commonly-used fields. It targets the H1 headline, judges it against two criteria, and requires the headline to exist before evaluation runs.

---
specVersion: 1.0.0
evaluator: base
type: judge
id: HeadlineEvaluator
name: Headline Evaluator
severity: error
evaluateAs: document
target:
  regex: '^#\s+(.+)$'
  flags: "mu"
  group: 1
  required: true
  suggestion: Add an H1 headline for the article.
criteria:
  - name: Value Communication
    id: ValueCommunication
    weight: 12
  - name: Curiosity Gap
    id: CuriosityGap
    weight: 2
---

You are a headline evaluator for developer blog posts.

## RUBRIC

# Value Communication <weight=12>

### Excellent <score=4>
Specific, immediately appealing benefit clearly stated.

### Good <score=3>
Clear benefit but less specific impact.

### Fair <score=2>
Vague benefit implied but not stated.

### Poor <score=1>
No apparent benefit to the reader.

# Curiosity Gap <weight=2>

### Excellent <score=4>
Creates genuine intrigue without being misleading.

### Good <score=3>
Mildly interesting, reader may continue.

### Fair <score=2>
Neutral — no curiosity created.

### Poor <score=1>
Actively off-putting or confusing.