Official plugins have YAML/XML syntax errors (agnix lint)

[longanisainhertaco]

Description

Running agnix (agent config linter, v0.17.0) against the official plugin directory reveals multiple syntax errors in Anthropic-maintained plugins. These cause agent frontmatter parse failures and may prevent skills from triggering correctly.

Errors Found

feature-dev (3 agent files)

tools: field uses comma-separated string instead of YAML list:

tools: Glob, Grep, LS, Read, NotebookRead, WebFetch, TodoWrite, WebSearch, KillShell, BashOutput

Should be:

tools:
  - Glob
  - Grep
  - LS
  ...

Files: code-architect.md, code-explorer.md, code-reviewer.md

hookify

• conversation-analyzer.md: YAML frontmatter parse error at line 3:124 ("mapping values are not allowed in this context")
• writing-rules/SKILL.md: Skill name writing-hookify-rules doesn't match parent directory writing-rules

pr-review-toolkit

• code-reviewer.md: YAML frontmatter parse error at line 3:717, unclosed <example> and <function> XML tags
• code-simplifier.md: Unclosed <example> and <function> XML tags

code-review

• code-review.md: Multiple unclosed <brief> and <file> XML tags

plugin-dev

• create-plugin.md: Unclosed <example> tag
• agent-development/SKILL.md: Unclosed <example> tag
• plugin-settings/SKILL.md: Windows path separators in backtick blocks
• skill-development/SKILL.md: File reference deeper than one level

claude-md-management

• templates.md: Multiple unclosed <purpose> and <structure> XML tags

Environment

• Claude Code: latest (March 2026)
• macOS Darwin 25.3.0 (Apple Silicon)
• agnix v0.17.0

Reproduction

npm install -g agnix
agnix ~/.claude/plugins/marketplaces/claude-plugins-official/

[yurukusa]

Good catch. Note that the comma-separated tools: format is actually valid in Claude Code — it's not standard YAML, but Claude Code's frontmatter parser handles both formats:

tools: Glob, Grep, Read     # comma-separated string
tools:                       # YAML list
  - Glob
  - Grep
  - Read

The parser converts comma-separated strings to arrays internally. So while the YAML list format is more correct per spec, the plugins do work at runtime.
The actual frontmatter parse error in conversation-analyzer.md ("mapping values not allowed") is a real bug though — likely a colon in an unquoted value.