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Claude Code Plugin Reference (night-market edition)

An author-facing reference for how Claude Code plugins, skills, commands, agents, and hooks actually behave, with verified contracts and re-verification commands.

Dev & CodingAdvanced★ 339⑂ 36AI score 8/10Last updated: Sep 24, 2026

What it does

  • Documents manifest fields (plugin.json, metadata.json, openpackage.yml, marketplace.json) and the local rules layered on them.
  • Spells out the SKILL.md frontmatter contract: 160-char description cap, role taxonomy, hub-and-spoke progressive loading, required Exit Criteria section.
  • Covers hook mechanics in depth: register only in hooks/hooks.json, read the payload from stdin JSON (never CLAUDE_TOOL_* env vars), per-event verdict JSON shapes, timeout budgets, and plugin-cache execution constraints.
  • Lists Python 3.9 host-interpreter landmines (datetime.UTC, bare unions, unguarded third-party imports) with the correct alternatives.
  • Ends with a checklist plus shell commands to re-verify every volatile claim.

Who it's for

  • Developers authoring or debugging Claude Code plugins, skills, and hooks.
  • Anyone chasing a hook that silently no-ops or gets killed by a timeout.
  • Contributors to the claude-night-market repo, where most of these conventions are enforced by ratchets and CI.

Examples

  1. A PreToolUse hook never blocks: check it parses stdin JSON and emits permissionDecision as exactly allow/deny/ask.
  2. Adding a new skill: verify it's in the plugin's skills array, description ≤160 chars, and has an ## Exit Criteria section before committing.
  3. A hook shelling out to a subprocess: assert in a test that the internal timeout is strictly less than the timeout registered in hooks.json.

· · · Install guide · · ·

Try it now, no install

Paste this into Claude to use the skill without installing anything.

Read the instructions in this file and follow them to help me:
https://raw.githubusercontent.com/athola/claude-night-market/HEAD/.claude/skills/claude-code-plugin-reference/SKILL.md

What I want: (describe your task here)

If Claude can't open the link, open it yourself and paste the contents instead.

↓ If it works for you, download the ZIP below and install it. Then it runs on its own — no pasting each time.

Install in the Claude app (no terminal)
  1. Download the ZIP with the button below.
  2. In Claude, open Settings → Capabilities and turn on 'Code execution and file creation'. (one time)
  3. Go to Customize → Skills → + → 'Upload a skill' and upload the ZIP.
↓ Download ZIP
Install in Claude Code

Let Claude do it — paste this into Claude Code

Install the skill I found on Claude Skill Mart.
Copy the .claude/skills/claude-code-plugin-reference folder from the GitHub repo athola/claude-night-market into my ~/.claude/skills/claude-code-plugin-reference/.
When it's done, tell me in one line what this skill can do.

Install with a command instead

git clone https://github.com/athola/claude-night-market.git && mkdir -p ~/.claude/skills && cp -r claude-night-market/.claude/skills/claude-code-plugin-reference ~/.claude/skills/

⚠ This is a third-party skill. Check the source repository before installing.

  1. Open a terminal and cd into a folder where you keep source checkouts.
  2. Clone the repo: git clone https://github.com/athola/claude-night-market.git
  3. Make sure the skills folder exists: mkdir -p ~/.claude/skills
  4. Copy the skill in: cp -r claude-night-market/.claude/skills/claude-code-plugin-reference ~/.claude/skills/
  5. Restart Claude Code, then ask something like "I'm writing a plugin hook — what are the rules?" to trigger the skill.
  6. Optional: to run the verification commands in the document, execute them from the cloned repo root, since they reference repo-local paths.
View source on GitHub ↗License: MIT