Plugins and Marketplaces

A Claude Code plugin is the unit that bundles scattered extensions into one package for distribution to teams and the community, and a marketplace is the catalog where those packages are discovered and installed. Seen through the harness lens, this is the distribution layer that packages the materials from the previous three documents — skills, hooks, MCP — into “one installable piece of harness”.

Background reference

This page is background material on Claude Code itself, the platform MoAI-ADK runs on. MoAI-ADK’s own features are covered in the sections above it in the sidebar.

Info

One-line summary: A plugin is an “extension bundle” that packs commands, agents, skills, hooks, and MCP into one folder, versioned and distributed — and a marketplace is the app store where you pick those bundles.

A plugin is a package that bundles multiple Claude Code extension elements into one directory for sharing, reuse, and versioning. Unlike standalone configuration placed directly in the .claude/ directory, a plugin has an identity via its manifest file and is distributed to other projects and teams through marketplaces.

The difference between standalone configuration and a plugin is clear-cut.

The heart of a plugin is the .claude-plugin/plugin.json manifest. This file defines the plugin’s name, description, and version, and the name field becomes the namespace prefix for its skills. The manifest is optional — a plugin works without one — but versioning and marketplace distribution are far easier with it.

{
  "name": "my-first-plugin",
  "description": "A greeting plugin to learn the basics",
  "version": "1.0.0",
  "author": { "name": "Your Name" }
}

version is optional. If specified, updates reach users only when you bump this value; if omitted and distributed via git, the commit SHA acts as the version and every commit is treated as a new version.

During development, load a local plugin without installing via claude --plugin-dir ./my-plugin, and after changes apply them without a restart via /reload-plugins.

Place per-element directories at the plugin root (the plugin directory itself, not .claude-plugin/). Important caution: .claude-plugin/ contains only plugin.json; all components — skills, commands, agents, hooks — live at the plugin root.

Because one plugin can carry skills, hooks, and MCP simultaneously, “every extension this job needs” arrives in a single install. For example, the commit-commands plugin bundles commit, push, and PR-creation skills, and pr-review-toolkit ships a set of agents dedicated to PR review.

A marketplace is a catalog holding a list of plugins someone has built. Usage is two steps: first add the catalog so you can browse it, then install individual plugins you want. Think of it as registering an app store versus downloading individual apps.

/plugin marketplace add accepts various sources.

# GitHub repository (owner/repo form)
/plugin marketplace add anthropics/claude-plugins-official

# Other Git hosts (.git suffix required)
/plugin marketplace add https://gitlab.com/company/plugins.git

# Pin a specific branch or tag
/plugin marketplace add https://gitlab.com/company/plugins.git#v1.0.0

# Local path / remote marketplace.json
/plugin marketplace add ./my-marketplace
/plugin marketplace add https://example.com/marketplace.json

The official Anthropic marketplace (claude-plugins-official) is automatically available when Claude Code starts. Community marketplaces are added manually.

# Install from the official marketplace
/plugin install hello@claude-plugins-official

# Add a community marketplace, then install
/plugin marketplace add anthropics/claude-plugins-community
/plugin install <plugin-name>@claude-plugins-community

Running /plugin opens the plugin manager with four tabs: Discover / Installed / Marketplaces / Errors. The detail panel in the Discover tab lets you preview, before installing, the estimated context cost, the last update date, and the list of commands, agents, skills, hooks, MCP, and LSP that will be installed.

There are three install scopes.

Install, enable, disable, and remove are also available via CLI.

/plugin install plugin-name@marketplace-name   # install (default user scope)
/plugin disable plugin-name@marketplace-name    # disable (does not remove)
/plugin enable  plugin-name@marketplace-name    # re-enable
/plugin uninstall plugin-name@marketplace-name  # remove entirely
/reload-plugins                                 # apply changes without a restart

At the team level, declare marketplaces under the extraKnownMarketplaces key in .claude/settings.json, and when a collaborator trusts the repository folder, Claude Code guides them through those marketplaces and plugin installs.

Code intelligence plugins activate Claude Code’s built-in code intelligence tools via LSP (Language Server Protocol) — the very technology underpinning code navigation in VS Code. Install the per-language plugin, and the corresponding language server binary must be present on the system for it to work.

With the plugin active, Claude gains two capabilities.

• Automatic diagnostics: every time Claude edits a file, the language server analyzes the change and automatically reports type errors, missing imports, and syntax errors. Without separately running a compiler or linter, Claude notices errors in the same turn and fixes them immediately. When “diagnostics found” appears, press Ctrl+O to view them inline.
• Code navigation: go to definition, find references, hover type info, symbol lists, find implementations, and call-hierarchy tracing. Far more precise navigation than grep-based search.

If an Executable not found in $PATH error shows in the /plugin Errors tab, install the language server binary from the table above. Note that rust-analyzer, pyright, and the like can use a lot of memory on a large codebase — if that is a burden, disable the plugin and rely on Claude’s built-in search.

Plugins and marketplaces are components requiring very high trust, because they can execute arbitrary code with your user permissions. Install only from sources you trust.

• Anthropic does not control the MCP servers, files, or software included in plugins, and does not verify they behave as intended. Review a third-party plugin’s homepage and the Discover tab’s “Will install” list yourself before installing.
• Community-marketplace plugins are distributed pinned to a specific commit SHA after passing Anthropic’s automated verification and safety screening. The final trust judgment still belongs to the installer.
• Organizations can restrict which marketplaces users may add via managed settings.

flowchart TD
    A[Add a marketplace
/plugin marketplace add] --> B[Browse plugins
/plugin Discover tab]
    B --> C{Do you trust
the source?}
    C -- No --> D[Hold off installing
Review homepage and Will install]
    C -- Yes --> E[Choose install scope
User / Project / Local]
    E --> F[Install
/plugin install]
    F --> G[Apply changes
/reload-plugins]
    G --> H[Use namespaced skills
/plugin-name:skill]

MoAI-ADK itself is not a plugin — moai init deploys harness assets (skills, agents, hooks, settings) directly into the .claude/ directory. Still, two things on this page apply directly to MoAI-ADK users. First, the context cost estimate in the Discover tab is a metric that reflects tokenomics thinking exactly — every time you install an extension, check how much always-on context it adds before deciding. Second, code intelligence (LSP) plugins are in the same family as the diagnostic signals MoAI-ADK’s per-language quality gates use, so installing the LSP plugin for your language makes the loop that catches type errors in the same turn as the edit much tighter.

• Skills
• Hooks
• MCP Servers

• Create plugins (code.claude.com)
• Discover and install plugins (code.claude.com)
• What Claude gains from code intelligence plugins

Tip

If a plugin you want to install is not visible, the marketplace may be stale. Refresh the list with /plugin marketplace update <marketplace-name> and try the install again.