Adds .claude-plugin/marketplace.json (one marketplace, one plugin, plugin
content = the whole repo root) and .claude-plugin/plugin.json, verified
against the current Agent Skills/plugin docs schema. Renamed SKILL.md's
frontmatter name from arbitrary-definitions to design-system so the
plugin invocation isn't a redundant doubled name — it's now
/arbitrary-definitions:design-system rather than
/arbitrary-definitions:arbitrary-definitions.

Install:
  /plugin marketplace add kejadlen/arbitrary-definitions-design-system
  /plugin install arbitrary-definitions@arbitrary-definitions

Updated README's install section to the plugin flow in place of the
manual git-clone-into-.claude/skills instructions.

diff --git a/.claude-plugin/marketplace.json b/.claude-plugin/marketplace.json
new file mode 100644
index 0000000..a2c71a8
--- /dev/null
+++ b/.claude-plugin/marketplace.json
@@ -0,0 +1,14 @@
+{
+  "name": "arbitrary-definitions",
+  "owner": {
+    "name": "kejadlen"
+  },
+  "plugins": [
+    {
+      "name": "arbitrary-definitions",
+      "source": "./",
+      "description": "Design tokens, component contracts, and voice guidance for the Arbitrary Definitions personal design system.",
+      "version": "1.0.0"
+    }
+  ]
+}
diff --git a/.claude-plugin/plugin.json b/.claude-plugin/plugin.json
new file mode 100644
index 0000000..2487d7f
--- /dev/null
+++ b/.claude-plugin/plugin.json
@@ -0,0 +1,8 @@
+{
+  "name": "arbitrary-definitions",
+  "displayName": "Arbitrary Definitions",
+  "description": "Design tokens, component contracts, and voice guidance for the Arbitrary Definitions personal design system — bare-element markup, one swappable accent, IBM Plex Mono labels, no CSS class API to memorize.",
+  "version": "1.0.0",
+  "homepage": "https://kejadlen.github.io/arbitrary-definitions-design-system/",
+  "repository": "https://github.com/kejadlen/arbitrary-definitions-design-system"
+}
diff --git a/README.md b/README.md
index f3216b3..be46576 100644
--- a/README.md
+++ b/README.md
@@ -93,16 +93,19 @@ Two files, in this order, and almost no JavaScript:
 Retheming means overriding a handful of custom properties after `tokens.css`
 loads — no recompile, no fork. See [Using the CSS](https://kejadlen.github.io/arbitrary-definitions-design-system/install/).
 
-## Claude Code skill
+## Claude Code plugin
 
-This repo doubles as a Claude Code skill — `SKILL.md` at the root, in the
-standard [Agent Skills](https://code.claude.com/docs/en/skills) format.
-Clone this repo into `.claude/skills/arbitrary-definitions/` in another
-project and Claude picks it up automatically, with the exact component
-contracts, tokens, and voice guidance to build new interfaces that look like
-they came from the same hand as this one:
+This repo is also a Claude Code plugin marketplace — `.claude-plugin/marketplace.json`
+and `.claude-plugin/plugin.json` at the root, wrapping the `SKILL.md` also at
+the root (the standard [Agent Skills](https://code.claude.com/docs/en/skills)
+format). Install it from anywhere:
 
 ```console
-$ git clone https://github.com/kejadlen/arbitrary-definitions-design-system \
-    .claude/skills/arbitrary-definitions
+$ claude
+> /plugin marketplace add kejadlen/arbitrary-definitions-design-system
+> /plugin install arbitrary-definitions@arbitrary-definitions
 ```
+
+Then invoke `/arbitrary-definitions:design-system` for the exact component
+contracts, tokens, and voice guidance to build new interfaces that look like
+they came from the same hand as this one.
diff --git a/SKILL.md b/SKILL.md
index 1a49a20..1074fd9 100644
--- a/SKILL.md
+++ b/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: arbitrary-definitions
+name: design-system
 description: Use this skill to build interfaces, pages, or prototypes in the Arbitrary Definitions style — a personal design system for self-hosted, single-user tools. Warm low-chroma neutrals, one swappable accent, IBM Plex Mono labels, and sixteen components built as plain HTML with no CSS class API to memorize. Use whenever a project should look like it came from the same hand as the others in this umbrella.
 user-invocable: true
 ---