PostCSS Config Validator

Validate PostCSS config files (.postcssrc, postcss.config.js, package.json#postcss) for plugin ordering, deprecated plugins, Tailwind integration, and best p...

Security Scan

The skill is internally consistent: it is a local PostCSS config linter that only reads project config files and reports issues, and it does not request credentials or install external software.

Purpose & Capability

Name/description (PostCSS config validation) match the included code and SKILL.md. The script parses JSON configs, inspects plugin lists and ordering, and reports findings consistent with the stated ruleset.

Instruction Scope

Runtime instructions tell the agent to run the bundled Python script against local PostCSS config files. The script reads files from the working directory (config files and package.json), which is appropriate and expected for this purpose. It does not instruct the agent to read unrelated system paths or transmit data externally.

Install Mechanism

No install spec; this is instruction-only with a bundled script. Execution requires Python 3.8+ and no external packages (script claims to use only the stdlib). No downloads or archive extraction are used.

Credentials

The skill requires no environment variables, credentials, or config paths beyond local project files. This is proportional to a linter that analyzes local PostCSS configs.

Persistence & Privilege

always is false and the skill does not request persistent system privileges or modify other skills. It runs on demand and does not declare autonomous elevation.

Assessment

This skill appears to be a straightforward, local PostCSS config linter. It will read files in the project directory (e.g., .postcssrc, postcss.config.js, package.json) to produce warnings/errors; that is expected behavior. Before running: ensure you're comfortable the agent can read the project files you point it at. The script claims no network activity or credentials; if you need extra assurance, inspect the full bundled Python file for any hidden I/O or network calls (the visible portions use only local file I/O and stdlib). Requires Python 3.8+ to run. If you only want static analysis and not to execute arbitrary scripts, consider running the included Python file locally in a sandbox or review the remaining parts of the script yourself prior to use.

Validate .postcssrc, .postcssrc.json, postcss.config.js, postcss.config.ts, and package.json#postcss for deprecated plugins, ordering issues, Tailwind integration problems, parser misconfiguration, and best practices. JS/TS configs are detected but cannot be statically validated. Supports text, JSON, and summary output formats with CI-friendly exit codes.

Commands

# Full validation (all 22+ rules)
python3 scripts/postcss_config_validator.py validate .postcssrc

# Quick structure-only check
python3 scripts/postcss_config_validator.py check .postcssrc.json

# Explain config in human-readable form
python3 scripts/postcss_config_validator.py explain package.json

# Suggest improvements
python3 scripts/postcss_config_validator.py suggest .postcssrc

# JSON output (CI-friendly)
python3 scripts/postcss_config_validator.py validate .postcssrc --format json

# Summary only (pass/fail + counts)
python3 scripts/postcss_config_validator.py validate .postcssrc --format summary

# Strict mode (warnings and infos become errors)
python3 scripts/postcss_config_validator.py validate .postcssrc --strict

Rules (22+)

#	ID	Category	Severity	Rule
1	S1	Structure	Error	File not found or unreadable
2	S2	Structure	Error	Empty config file
3	S3	Structure	Error	Invalid JSON syntax
4	S4	Structure	Warning	Unknown top-level keys (valid: plugins, parser, syntax, stringifier, map, from, to)
5	S5	Structure	Info	JS/TS config detected — cannot statically validate
6	P1	Plugins	Warning	Empty plugins object/array
7	P2	Plugins	Warning	Deprecated plugin (autoprefixer-core, postcss-cssnext, lost, postcss-sprites)
8	P3	Plugins	Warning	Duplicate plugins
9	P4	Plugins	Info	Plugin ordering issues (autoprefixer after preset-env, cssnano last)
10	P5	Plugins	Info	postcss-import should be first plugin
11	P6	Plugins	Info	Unknown/uncommon plugin name (not in top 50 list)
12	T1	Tailwind	Info	tailwindcss without nesting plugin
13	T2	Tailwind	Warning	tailwindcss after autoprefixer (wrong order)
14	T3	Tailwind	Info	postcss-preset-env with tailwindcss (potential conflict)
15	X1	Syntax/Parser	Warning	Both parser and syntax specified
16	X2	Syntax/Parser	Info	Unknown parser value
17	X3	Syntax/Parser	Info	Parser set but no matching preprocessor plugin
18	M1	Source Maps	Info	Source maps disabled (map: false)
19	M2	Source Maps	Info	Inline source maps enabled (map.inline: true)
20	B1	Best Practices	Warning	No plugins configured
21	B2	Best Practices	Info	Using postcss-preset-env AND individual feature plugins it includes
22	B3	Best Practices	Info	Very large number of plugins (>15)

Output Formats

• text (default): Human-readable with severity icons
• json: Machine-parseable JSON with findings array and summary
• summary: Pass/fail with error/warning/info counts

Exit Codes

• 0: No errors (warnings/infos only or clean)
• 1: One or more errors found
• 2: File not found or invalid input

Requirements

• Python 3.8+
• No external dependencies (pure stdlib)