[Feature]: Add marketplace-structure skill for plugin marketplace creation

[sjnims]

Problem or Need

Users asking to "create a marketplace", "organize multiple plugins", or "distribute plugins" currently have no dedicated skill guidance. The plugin-structure skill only mentions "marketplace" incidentally (as an installation method) and doesn't cover:

• marketplace.json schema and required fields
• Multi-plugin organization within a marketplace
• Plugin source types (GitHub, git URLs, relative paths)
• Distribution strategies (GitHub hosting, team settings)
• The strict vs. non-strict mode distinction
• Relationship between marketplace entries and plugin.json

This is a significant gap since this repository itself is a marketplace and serves as a reference implementation.

Proposed Solution

Create a new marketplace-structure skill with comprehensive guidance for creating and maintaining plugin marketplaces.

Skill Structure

skills/marketplace-structure/
├── SKILL.md (~1,800 words)
├── references/
│   ├── schema-reference.md      # Complete marketplace.json field reference
│   └── distribution-patterns.md  # Hosting strategies, team setup
└── examples/
    ├── minimal-marketplace.md    # Single plugin marketplace
    ├── team-marketplace.md       # Internal company marketplace
    └── community-marketplace.md  # Public multi-plugin marketplace

SKILL.md Content Outline

1. Overview - What marketplaces are, when to create one vs. just a plugin
2. Directory Structure - Where marketplace.json goes (.claude-plugin/)
3. Marketplace Schema - Core fields (name, owner, metadata, plugins)
4. Plugin Entry Format - Required and optional fields for plugin entries
5. Plugin Sources - Relative paths, GitHub repos, git URLs
6. strict vs. non-strict mode - When plugin.json is required
7. Best Practices - Organization, versioning, distribution
8. Additional Resources - Links to references/examples

Trigger Phrases for Description

description: This skill should be used when the user asks to "create a marketplace", 
"set up marketplace.json", "organize multiple plugins", "distribute plugins", 
"host plugins", "marketplace schema", or needs guidance on plugin marketplace 
structure, multi-plugin organization, or plugin distribution strategies.

Which component would this affect?

Skill

Specific Component (if applicable)

New skill: marketplace-structure (to be created in plugins/plugin-dev/skills/)

Alternatives Considered

1. Add marketplace content to plugin-structure skill - Rejected because:

   • Different abstraction level (marketplace contains multiple plugins)
   • Different target audience (marketplace maintainers vs. plugin developers)
   • Would bloat the skill beyond the recommended 2,000 word limit
   • Different trigger conditions

2. Add to plugin-settings skill - Rejected because plugin-settings is about per-project .local.md configuration, not marketplace setup

3. Document only in README - Rejected because this is actionable guidance that should be model-invoked when users ask about marketplaces

Additional Context

Reference Material

• Official docs: https://code.claude.com/docs/en/plugin-marketplaces.md
• This repo's marketplace.json can serve as a real-world example
• Should cross-reference plugin-structure for plugin.json details (avoid duplication)

Relationship to Existing Skills

Skill	Relationship
plugin-structure	Complementary - covers individual plugins, this covers hosting multiple
mcp-integration	Reference only - marketplace entries can include mcpServers
hook-development	Reference only - marketplace entries can include hooks

Official Schema Reference

From official docs, marketplace.json requires:

• name (string) - Marketplace identifier
• owner (object) - Maintainer information
• plugins (array) - List of available plugins

Plugin entries require:

• name (string) - Plugin identifier
• source (string|object) - Where to fetch the plugin

How important is this feature to you?

Medium - Would be nice to have

[sjnims]

Related Component Enhancements

The marketplace-structure skill should integrate with existing plugin-dev components to create a cohesive development experience:

1. Extend plugin-validator agent for marketplace validation

Current scope: Only validates individual plugin structure
Proposed enhancement: When marketplace.json is detected, also validate:

• Marketplace schema (name, owner, plugins array required)
• Plugin entry completeness (name, source required per entry)
• Relative source paths actually exist
• strict mode compliance (plugin.json present when strict: true or omitted)
• No duplicate plugin names in the plugins array

Trigger phrase additions for description:

"validate marketplace", "check marketplace.json", "verify marketplace structure"

2. New /plugin-dev:create-marketplace command

Guided workflow paralleling /plugin-dev:create-plugin:

Phase	Purpose
1. Discovery	Marketplace purpose, target audience, single vs. multi-plugin
2. Plugin Planning	Which plugins to include, sources (relative, GitHub, git URL)
3. Metadata	Name, owner info, description, version
4. Structure Creation	Create .claude-plugin/marketplace.json, plugins/ directory
5. Plugin Entries	Configure each plugin entry with appropriate source
6. Distribution	GitHub hosting setup, team settings documentation
7. Validation	Run enhanced plugin-validator on marketplace
8. Testing	Add marketplace locally, install test plugin

3. Enhance /plugin-dev:create-plugin Phase 8

Current: Shallow reference: "Add marketplace entry (if publishing)"
Proposed enhancement:

• Load marketplace-structure skill when user wants to publish
• Guide through complete plugin entry creation for marketplace.json
• Validate entry against marketplace schema
• Show diff of marketplace.json before/after addition

4. Cross-references in marketplace-structure skill

The SKILL.md should reference:

Component	Reference Purpose
plugin-validator agent	For validating marketplace structure
/plugin-dev:create-marketplace	For guided marketplace creation
plugin-structure skill	For individual plugin.json details
This repository	As a working marketplace example

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This creates an integrated experience where the skill provides knowledge, the command provides workflow, and the agent provides validation—all working together for marketplace development.

[sjnims]

PR submitted: #89