Marketplace Dev

marketplace-dev

Convert a Claude Code skills repository into an official plugin marketplace so users can install skills via claude plugin marketplace add and get auto-updates.

Input: a repo with skills/ directories containing SKILL.md files. Output: .claude-plugin/marketplace.json + validated + installation-tested + PR-ready.

Phase 0: Evidence Intake

Before editing an existing marketplace, collect evidence instead of relying on the default template:

1. Read the current .claude-plugin/marketplace.json.
2. Read this repo's marketplace rules (CLAUDE.md, README install section, changelog).
3. Read official docs for marketplace/plugin path semantics.
4. If refining from prior failures, mine local Claude Code session history.

Each project's sessions live under ~/.claude/projects/<escaped-cwd>/:

• Top-level files: <session-id>.jsonl
• Subagent transcripts: <session-id>/subagents/agent-*.jsonl

Useful search patterns (adjust keywords to the failure you are debugging):

grep -lc "marketplace.json\|claude plugin validate\|claude plugin install" \
  ~/.claude/projects/<escaped-cwd>/*.jsonl
grep -lc "Unrecognized key\|Plugin not found\|No manifest found\|Duplicate plugin" \
  ~/.claude/projects/<escaped-cwd>/*.jsonl \
  ~/.claude/projects/<escaped-cwd>/*/subagents/*.jsonl

Extract lessons as evidence-backed rules: command attempted, observed output, root cause, final working command/config. Do not encode guesses from memory.

Phase 1: Analyze the Target Repo

Step 1: Discover all skills

# Find every SKILL.md
find <repo-path>/skills -name "SKILL.md" -type f 2>/dev/null

For each skill, extract from SKILL.md frontmatter:

• name — the skill identifier
• description — the ORIGINAL text, do NOT rewrite or translate

Step 2: Read the repo metadata

• VERSION file (if exists) — this becomes metadata.version
• README.md — understand the project, author info, categories
• LICENSE — note the license type
• Git remotes — identify upstream vs fork (git remote -v)

Step 3: Determine categories

Group skills by function. Categories are freeform strings. Good patterns:

• business-diagnostics, content-creation, thinking-tools, utilities
• developer-tools, productivity, documentation, security

Ask the user to confirm categories if grouping is ambiguous.

Step 4: Choose plugin boundaries

Claude Code has three separate levels:

marketplace -> plugin -> skill

• Marketplace name is used for install identity: plugin@marketplace.
• Plugin name is the slash namespace: /plugin-name:skill-name.
• Skill name comes from SKILL.md frontmatter when the skill path points to a directory containing SKILL.md directly.

Choose each plugin boundary by installation/update/cache intent:

• Single-skill plugin: use when the skill should install, update, and roll back independently with a narrow cache.
• Suite plugin: use when related skills should share one namespace and one install command, for example /daymade-docs:mermaid-tools.

For detailed source/cache patterns and pitfalls, read references/cache_and_source_patterns.md before changing source or skills.

Phase 2: Create marketplace.json

The official schema (memorize this)

Read references/marketplace_schema.md for the complete field reference. Key rules that are NOT obvious from the docs:

1. $schema field is REJECTED by claude plugin validate. Do not include it.
2. metadata only has 3 valid fields: description, version, pluginRoot. Nothing else. metadata.homepage does NOT exist — the validator accepts it silently but it's not in the spec.
3. metadata.version is the marketplace catalog version, NOT individual plugin versions. It should match the repo's VERSION file (e.g., "2.3.0").
4. Plugin entry version is independent. For first-time marketplace registration, use "1.0.0".
5. strict: false is required when there's no plugin.json in the repo. With strict: false, the marketplace entry IS the entire plugin definition. Having BOTH strict: false AND a plugin.json with components causes a load failure.
6. source defines the installed plugin root. For single-skill plugins, point source directly at the skill directory (e.g., "./tunnel-doctor") and omit skills entirely — this is the official pattern used by 167/168 plugins in anthropics/claude-plugins-official. For suite plugins, use source: "./<suite>" with explicit skills array listing subdirectories. Avoid source: "./" (installs full repo as cache) and skills: ["./"] (rejected by Claude Code 2.1.x path-escape validator).
7. Reserved marketplace names that CANNOT be used: claude-code-marketplace, claude-code-plugins, claude-plugins-official, anthropic-marketplace, anthropic-plugins, agent-skills, knowledge-work-plugins, life-sciences.
8. tags vs keywords: Both are optional. In the current Claude Code source, keywords is defined but never consumed in search. tags only has a UI effect for the value "community-managed" (shows a label). Neither affects discovery. The Discover tab searches only name + description + marketplaceName. Include keywords for future-proofing but don't over-invest.

Generate the marketplace.json

Use this template, filling in from the analysis:

{
  "name": "<marketplace-name>",
  "owner": {
    "name": "<github-org-or-username>"
  },
  "metadata": {
    "description": "<one-line description of the marketplace>",
    "version": "<from-VERSION-file-or-1.0.0>"
  },
  "plugins": [
    {
      "name": "<skill-name>",
      "description": "<EXACT text from SKILL.md frontmatter, do NOT rewrite>",
      "source": "./<skill-name>",
      "strict": false,
      "version": "1.0.0",
      "category": "<category>",
      "keywords": ["<relevant>", "<keywords>"]
    }
  ]
}

Naming the marketplace

The name field is what users type after @ in install commands: claude plugin install dbs@<marketplace-name>

Choose a name that is:

• Short and memorable
• kebab-case (lowercase, hyphens only)
• Related to the project identity, not generic

Description rules

• Use the ORIGINAL description from each SKILL.md frontmatter
• Do NOT translate, embellish, or "improve" descriptions
• If the repo's audience is Chinese, keep descriptions in Chinese
• If bilingual, use the first language in the SKILL.md description field
• The metadata.description at marketplace level can be a new summary

Maintaining an existing marketplace

When adding a new plugin to an existing marketplace.json:

1. Bump metadata.version — this is the marketplace catalog version. Follow semver: new plugin = minor bump, breaking change = major bump.
2. Update metadata.description — append the new skill's summary.
3. Set new plugin version to "1.0.0" — it's new to the marketplace.
4. Bump existing plugin version when its SKILL.md content changes. Claude Code uses version to detect updates — same version = skip update.
5. Bump existing plugin version when its source or skills changes. The installed cache path and component resolution changed even if SKILL.md did not.
6. Audit metadata for invalid fields — metadata.homepage is a common mistake (not in spec, silently ignored). Remove if found.

Phase 3: Validate

Step 1: One-shot pre-flight check

Run the bundled validator. It runs four checks in sequence and exits non-zero on any required failure:

bash scripts/check_marketplace.sh          # validates current repo
bash scripts/check_marketplace.sh /path    # validates a target repo

What it checks:

Common schema failures and fixes:

• Unrecognized key: "$schema" → remove the $schema field
• Duplicate plugin name → ensure all names are unique
• Path contains ".." → use ./ relative paths only
• No manifest found in directory when validating an installed cache path → validate the marketplace manifest or plugin source, not a strict: false cache directory.

Step 2: Installation test

# Add as local marketplace
claude plugin marketplace add .

# Install a plugin
claude plugin install <plugin-name>@<marketplace-name>

# Verify it appears
claude plugin list | grep <plugin-name>

# Check for updates (should say "already at latest")
claude plugin update <plugin-name>@<marketplace-name>

# Clean up
claude plugin uninstall <plugin-name>@<marketplace-name>
claude plugin marketplace remove <marketplace-name>

Step 3: Cache footprint test

After installation or update, inspect the actual cache. This is the only way to confirm source produced the intended snapshot:

PLUGIN=<plugin-name>
MARKET=<marketplace-name>
CACHE=$(jq -r --arg id "$PLUGIN@$MARKET" '.plugins[$id][0].installPath' ~/.claude/plugins/installed_plugins.json)
find "$CACHE" -maxdepth 1 -mindepth 1 -exec basename {} \; | sort

Expected results:

• Single-skill plugin cache: SKILL.md plus its own scripts/, references/, assets/ as applicable.
• Suite plugin cache: only the suite member skill directories and suite-scoped resources.
• If unrelated skill directories appear, source is too broad.
• If cache entries are symlinks, the plugin is not self-contained; use canonical source directories instead of symlink farms.

Step 4: GitHub installation test (if pushed)

# Test from GitHub (requires the branch to be pushed)
claude plugin marketplace add <github-user>/<repo>
claude plugin install <plugin-name>@<marketplace-name>

# Verify
claude plugin list | grep <plugin-name>

# Clean up
claude plugin uninstall <plugin-name>@<marketplace-name>
claude plugin marketplace remove <marketplace-name>

Pre-flight Checklist (MUST pass before proceeding to PR)

Run this checklist after every marketplace.json change. Do not skip items.

Automated checks

bash scripts/check_marketplace.sh

All four checks must pass. Treat the reverse-sync WARN as a real signal: an unregistered SKILL.md on disk is almost always either an accidentally-dropped skill you forgot to register, or dead code that should be removed.

Metadata check

Verify these by reading marketplace.json:

• metadata.version bumped from previous version
• metadata.description mentions all skill categories
• No metadata.homepage (not in spec, silently ignored)
• No $schema field (rejected by validator)

Per-plugin check

For each plugin entry:

• description matches SKILL.md frontmatter EXACTLY (not rewritten)
• version is "1.0.0" for new plugins, bumped for changed plugins
• source points directly at the skill directory (e.g., "./skill-name")
• Single-skill plugins omit the skills field (auto-discovery from source)
• Suite plugins list skills paths relative to source
• strict is false (no plugin.json in repo)
• name is kebab-case, unique across all entries

Final validation

bash scripts/check_marketplace.sh

Must print RESULT: PASSED before creating a PR. A WARN [4/4] is acceptable only when you have consciously decided to leave a SKILL.md unregistered.

Phase 4: Create PR

Principles

• Pure incremental: do NOT modify any existing files (skills, README, etc.)
• Squash commits: avoid binary bloat in git history from iterative changes
• Only add: .claude-plugin/marketplace.json, optionally scripts/, optionally update README

README update (if appropriate)

Add the marketplace install method above existing install instructions:

## Install

![demo](demo.gif)  <!-- only if demo exists -->

**Claude Code plugin marketplace (one-click install, auto-update):**

\`\`\`bash
claude plugin marketplace add <owner>/<repo>
claude plugin install <skill>@<marketplace-name>
\`\`\`

PR description template

Include:

• What was added (marketplace.json with N skills, M categories)
• Install commands users will use after merge
• Design decisions (pure incremental, original descriptions, etc.)
• Validation evidence (claude plugin validate . passed)
• Test plan (install commands to verify)

Bundled hooks (optional, auto-activated)

This skill ships two PostToolUse hooks under hooks/:

• hooks/post_edit_validate.sh — runs claude plugin validate whenever a marketplace.json file is written or edited.
• hooks/post_edit_sync_check.sh — warns when a SKILL.md is edited but the matching plugin entry in marketplace.json does not bump its version.

Both hooks are declared in this plugin's own manifest entry (plugins[].hooks), so they activate automatically when the plugin is enabled in a Claude Code session. No manual settings.json edit is required. To disable them, remove the hooks block from this plugin entry in the user's installed copy or use /plugin disable marketplace-dev (they take effect only when the plugin is enabled).

These hooks are editor-time guardrails. They do NOT replace scripts/check_marketplace.sh — always run the pre-flight check before a PR.

Anti-Patterns (things that went wrong and how to fix them)

Read references/anti_patterns.md for the full list of pitfalls discovered during real marketplace development. These are NOT theoretical — every one was encountered and debugged in production.