write-lint-rules

Find it fast

sed -n '<from>,<to>p' SKILL.md one section rather than reading the file; ./mxcli syntax <topic> answers how do I write this for a fraction of either.

lines	section
25-67	Rule File Structure
68-161	Available Query Functions
162-600	Object Properties
601-613	Helper Functions
614-700	Common Patterns
701-710	Validation

Writing Custom Starlark Lint Rules

Custom lint rules are written in Starlark (a Python-like language) and placed in .claude/lint-rules/ as .star files. They run alongside the built-in rules when mxcli lint -p app.mpr is executed.

Rule File Structure

Every .star file must define metadata constants and a check() function:

RULE_ID = "CUSTOM001"          # unique identifier
RULE_NAME = "MyRule"           # Short display name
DESCRIPTION = "What it checks" # One-line description
CATEGORY = "security"          # Category: naming, quality, design, security, etc.
SEVERITY = "warning"           # hint, info, warning, error

def check():
    violations = []
    # ... iterate data, find issues, append violations ...
    return violations

Catalog data requirements (widgets, refs_to, cycles, …)

Some builtins need a deeper catalog than the default fast build:

• refs_to, refs_from, widgets, xpath_expressions, activities_for, permissions, permissions_for, strings and the widget_count field of a page or snippet need REFRESH CATALOG FULL — the refs, widgets, xpath_expressions, activities, permissions and strings tables and the widget counts are only written by a full build.
• The graph-analysis builtins (cycles, module_dependencies, community_of, layer_of, centrality, god_nodes, integration_surface) need REFRESH CATALOG COMMUNITIES (the graph_* tables).

You don't have to do anything: mxcli lint (and the LINT statement) auto-detect these builtins (a call name() and .widget_count in your rule's source and build the catalog at the required depth automatically. If the scan cannot see it — e.g. getattr(p, "widget_count"), or a builtin passed around by name — or you want to be explicit, declare it: