diff --git a/.github/schemas/plugin-manifest.schema.json b/.github/schemas/plugin-manifest.schema.json
new file mode 100644
index 0000000..16d74fa
--- /dev/null
+++ b/.github/schemas/plugin-manifest.schema.json
@@ -0,0 +1,96 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "title": "Claude Code Plugin Manifest",
+  "description": "Schema for .claude-plugin/plugin.json files, based on https://code.claude.com/docs/en/plugins-reference",
+  "type": "object",
+  "required": ["name"],
+  "additionalProperties": false,
+  "$defs": {
+    "stringOrStringArray": {
+      "oneOf": [
+        { "type": "string" },
+        { "type": "array", "items": { "type": "string" } }
+      ]
+    },
+    "stringOrArrayOrObject": {
+      "oneOf": [
+        { "type": "string" },
+        { "type": "array", "items": { "type": "string" } },
+        { "type": "object" }
+      ]
+    }
+  },
+  "properties": {
+    "name": {
+      "type": "string",
+      "description": "Unique plugin identifier (kebab-case, no spaces)"
+    },
+    "displayName": {
+      "type": "string",
+      "description": "Human-readable plugin name for marketplace display"
+    },
+    "version": {
+      "type": "string",
+      "description": "Semantic version (MAJOR.MINOR.PATCH)"
+    },
+    "description": {
+      "type": "string",
+      "description": "Brief explanation of plugin purpose"
+    },
+    "author": {
+      "type": "object",
+      "description": "Author information",
+      "properties": {
+        "name": { "type": "string" },
+        "email": { "type": "string" },
+        "url": { "type": "string" }
+      },
+      "additionalProperties": false
+    },
+    "homepage": {
+      "type": "string",
+      "description": "Documentation URL"
+    },
+    "repository": {
+      "type": "string",
+      "description": "Source code URL"
+    },
+    "license": {
+      "type": "string",
+      "description": "License identifier (e.g. MIT, Apache-2.0)"
+    },
+    "keywords": {
+      "type": "array",
+      "items": { "type": "string" },
+      "description": "Discovery tags"
+    },
+    "commands": {
+      "$ref": "#/$defs/stringOrStringArray",
+      "description": "Additional command files/directories (string or array of strings)"
+    },
+    "agents": {
+      "$ref": "#/$defs/stringOrStringArray",
+      "description": "Additional agent files/directories (string or array of strings)"
+    },
+    "skills": {
+      "$ref": "#/$defs/stringOrStringArray",
+      "description": "Additional skill directories (string or array of strings)"
+    },
+    "hooks": {
+      "$ref": "#/$defs/stringOrArrayOrObject",
+      "description": "Hook config paths or inline hook configuration (string, array, or object)"
+    },
+    "mcpServers": {
+      "$ref": "#/$defs/stringOrArrayOrObject",
+      "description": "MCP server config paths or inline configuration (string, array, or object)"
+    },
+    "outputStyles": {
+      "$ref": "#/$defs/stringOrStringArray",
+      "description": "Additional output style files/directories (string or array of strings)"
+    },
+    "lspServers": {
+      "$ref": "#/$defs/stringOrArrayOrObject",
+      "description": "LSP server config paths or inline configuration (string, array, or object)"
+    }
+  }
+}
diff --git a/.github/scripts/validate-frontmatter.py b/.github/scripts/validate-frontmatter.py
new file mode 100644
index 0000000..16db874
--- /dev/null
+++ b/.github/scripts/validate-frontmatter.py
@@ -0,0 +1,103 @@
+#!/usr/bin/env python3
+"""Validate YAML frontmatter in markdown files and standalone YAML files under plugins/."""
+
+import os
+import subprocess
+import sys
+import tempfile
+
+PLUGINS_DIR = "plugins"
+YAMLLINT_CONFIG = ".yamllint.yml"
+
+
+def extract_frontmatter(filepath: str) -> tuple[str | None, int]:
+    """Extract YAML frontmatter from a markdown file.
+
+    Returns (frontmatter_content, start_line) or (None, 0) if no frontmatter.
+    """
+    with open(filepath, "r") as f:
+        lines = f.readlines()
+
+    if not lines or lines[0].rstrip("\n") != "---":
+        return None, 0
+
+    end = None
+    for i in range(1, len(lines)):
+        if lines[i].rstrip("\n") == "---":
+            end = i
+            break
+
+    if end is None:
+        return None, 0
+
+    # Return frontmatter content (between the two --- delimiters)
+    return "".join(lines[1:end]), 1
+
+
+def run_yamllint(content: str, original_file: str, line_offset: int) -> list[str]:
+    """Run yamllint on content and return error messages with adjusted line numbers."""
+    errors = []
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".yml", delete=False) as tmp:
+        tmp.write(content)
+        tmp_path = tmp.name
+
+    try:
+        result = subprocess.run(
+            ["yamllint", "-c", YAMLLINT_CONFIG, tmp_path],
+            capture_output=True,
+            text=True,
+        )
+        if result.returncode != 0:
+            for line in result.stdout.strip().splitlines():
+                # yamllint output format: "file:line:col: [level] message"
+                if tmp_path in line:
+                    # Replace temp path with original file path and adjust line number
+                    rest = line.split(tmp_path, 1)[1]
+                    if rest.startswith(":"):
+                        parts = rest[1:].split(":", 2)
+                        if len(parts) >= 2 and parts[0].strip().isdigit():
+                            adjusted_line = int(parts[0].strip()) + line_offset
+                            errors.append(
+                                f"{original_file}:{adjusted_line}:{':'.join(parts[1:])}"
+                            )
+                            continue
+                    errors.append(f"{original_file}{rest}")
+    finally:
+        os.unlink(tmp_path)
+
+    return errors
+
+
+def main() -> int:
+    all_errors: list[str] = []
+
+    # Find all markdown files with frontmatter
+    for root, _dirs, files in os.walk(PLUGINS_DIR):
+        for filename in files:
+            filepath = os.path.join(root, filename)
+
+            if filename.endswith(".md"):
+                frontmatter, offset = extract_frontmatter(filepath)
+                if frontmatter is not None:
+                    errors = run_yamllint(frontmatter, filepath, offset)
+                    all_errors.extend(errors)
+
+            elif filename.endswith((".yml", ".yaml")):
+                with open(filepath) as f:
+                    content = f.read()
+                errors = run_yamllint(content, filepath, 0)
+                all_errors.extend(errors)
+
+    if all_errors:
+        print("YAML validation errors found:\n")
+        for error in all_errors:
+            print(f"  {error}")
+        print(f"\n{len(all_errors)} error(s) found.")
+        return 1
+
+    print("All YAML frontmatter and YAML files are valid.")
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/.github/scripts/validate-marketplace.py b/.github/scripts/validate-marketplace.py
new file mode 100644
index 0000000..aa12918
--- /dev/null
+++ b/.github/scripts/validate-marketplace.py
@@ -0,0 +1,173 @@
+#!/usr/bin/env python3
+"""Validate marketplace.json registry against the actual plugin directories."""
+
+from __future__ import annotations
+
+import json
+import sys
+from pathlib import Path
+
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+MARKETPLACE_JSON = REPO_ROOT / ".claude-plugin" / "marketplace.json"
+PLUGINS_DIR = REPO_ROOT / "plugins"
+
+
+def load_marketplace() -> dict | None:
+    """Load and return the parsed marketplace.json, or None on parse error."""
+    with MARKETPLACE_JSON.open() as f:
+        try:
+            return json.load(f)
+        except json.JSONDecodeError as exc:
+            print(f"\n✗ Failed to parse marketplace.json: {exc}")
+            return None
+
+
+def _resolve_source(plugin: dict) -> Path:
+    """Resolve a plugin's source path to an absolute path under REPO_ROOT."""
+    return REPO_ROOT / plugin["source"].removeprefix("./")
+
+
+def check_source_paths(plugins: list[dict]) -> list[str]:
+    """Check that every plugin source path exists as a directory."""
+    errors: list[str] = []
+    for plugin in plugins:
+        name = plugin["name"]
+        source = _resolve_source(plugin)
+        if not source.is_dir():
+            errors.append(f"  ✗ Plugin '{name}': source path does not exist: {plugin['source']}")
+    return errors
+
+
+def check_duplicate_names(plugins: list[dict]) -> list[str]:
+    """Check for duplicate plugin names in marketplace.json."""
+    errors: list[str] = []
+    seen: dict[str, int] = {}
+    for plugin in plugins:
+        name = plugin["name"]
+        seen[name] = seen.get(name, 0) + 1
+    for name, count in seen.items():
+        if count > 1:
+            errors.append(f"  ✗ Plugin name '{name}' appears {count} times")
+    return errors
+
+
+def check_orphan_directories(plugins: list[dict]) -> list[str]:
+    """Find plugin directories not registered in marketplace.json."""
+    warnings: list[str] = []
+
+    # Resolve all registered source paths to absolute paths
+    registered: set[Path] = set()
+    for plugin in plugins:
+        registered.add(_resolve_source(plugin).resolve())
+
+    # Walk immediate children and known subdirectories of plugins/
+    plugin_dirs: list[Path] = []
+    if PLUGINS_DIR.is_dir():
+        for child in sorted(PLUGINS_DIR.iterdir()):
+            if not child.is_dir():
+                continue
+            # Some plugins live in subdirectories (e.g. plugins/commands/*, plugins/mcps/*)
+            has_plugin_json = (child / ".claude-plugin" / "plugin.json").exists()
+            has_subdirs = any(sub.is_dir() for sub in child.iterdir())
+            if has_plugin_json:
+                plugin_dirs.append(child)
+            elif has_subdirs:
+                # Check nested directories (e.g. plugins/commands/carta-devtools)
+                for sub in sorted(child.iterdir()):
+                    if sub.is_dir() and (sub / ".claude-plugin" / "plugin.json").exists():
+                        plugin_dirs.append(sub)
+            else:
+                plugin_dirs.append(child)
+
+    for d in plugin_dirs:
+        if d.resolve() not in registered:
+            rel = d.relative_to(REPO_ROOT)
+            warnings.append(f"  ! Directory '{rel}' is not registered in marketplace.json")
+
+    return warnings
+
+
+def check_required_files(plugins: list[dict]) -> list[str]:
+    """Check that each registered plugin has the required plugin.json."""
+    errors: list[str] = []
+    for plugin in plugins:
+        name = plugin["name"]
+        source = _resolve_source(plugin)
+        manifest = source / ".claude-plugin" / "plugin.json"
+        if not manifest.is_file():
+            errors.append(f"  ✗ Plugin '{name}': missing .claude-plugin/plugin.json")
+    return errors
+
+
+def main() -> int:
+    print("=" * 60)
+    print("Marketplace Validation")
+    print("=" * 60)
+
+    if not MARKETPLACE_JSON.is_file():
+        print(f"\n✗ marketplace.json not found at {MARKETPLACE_JSON}")
+        return 1
+
+    data = load_marketplace()
+    if data is None:
+        return 1
+    plugins = data.get("plugins", [])
+
+    error_count = 0
+    warning_count = 0
+
+    # Check 1: Source paths exist
+    print("\n--- Check 1: Source paths exist ---")
+    errors = check_source_paths(plugins)
+    if errors:
+        for e in errors:
+            print(e)
+        error_count += len(errors)
+    else:
+        print("  ✓ All source paths exist")
+
+    # Check 2: No duplicate plugin names
+    print("\n--- Check 2: No duplicate plugin names ---")
+    errors = check_duplicate_names(plugins)
+    if errors:
+        for e in errors:
+            print(e)
+        error_count += len(errors)
+    else:
+        print("  ✓ All plugin names are unique")
+
+    # Check 3: Orphan plugin directories
+    print("\n--- Check 3: Orphan plugin directories ---")
+    warnings = check_orphan_directories(plugins)
+    if warnings:
+        for w in warnings:
+            print(w)
+        warning_count += len(warnings)
+    else:
+        print("  ✓ No orphan plugin directories found")
+
+    # Check 4: Required files
+    print("\n--- Check 4: Required files ---")
+    errors = check_required_files(plugins)
+    if errors:
+        for e in errors:
+            print(e)
+        error_count += len(errors)
+    else:
+        print("  ✓ All plugins have required files")
+
+    # Summary
+    print("\n" + "=" * 60)
+    print(f"Summary: {error_count} error(s), {warning_count} warning(s)")
+    if error_count:
+        print("FAILED")
+    else:
+        print("PASSED")
+    print("=" * 60)
+
+    return 1 if error_count else 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())
diff --git a/.github/workflows/validate.yml b/.github/workflows/validate.yml
new file mode 100644
index 0000000..243237b
--- /dev/null
+++ b/.github/workflows/validate.yml
@@ -0,0 +1,37 @@
+name: Validate Plugins
+on:
+  pull_request:
+
+jobs:
+  validate:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Check for plugin changes
+        id: filter
+        run: |
+          CHANGED=$(gh pr diff ${{ github.event.pull_request.number }} --name-only | grep -c '^plugins/\|^\.claude-plugin/marketplace\.json\|^\.github/schemas/\|^\.github/scripts/\|^\.github/workflows/validate\.yml' || true)
+          echo "has_plugin_changes=$([ "$CHANGED" -gt 0 ] && echo true || echo false)" >> "$GITHUB_OUTPUT"
+        env:
+          GH_TOKEN: ${{ github.token }}
+      - uses: actions/setup-python@v5
+        if: steps.filter.outputs.has_plugin_changes == 'true'
+        with:
+          python-version: '3.12'
+      - run: pip install yamllint check-jsonschema
+        if: steps.filter.outputs.has_plugin_changes == 'true'
+      - name: Validate command frontmatter
+        if: steps.filter.outputs.has_plugin_changes == 'true'
+        run: python .github/scripts/validate-frontmatter.py
+      - name: Validate plugin manifests
+        if: steps.filter.outputs.has_plugin_changes == 'true'
+        run: |
+          manifests=$(find plugins -name "plugin.json" -path "*/.claude-plugin/*")
+          if [ -z "$manifests" ]; then
+            echo "ERROR: No plugin manifests found. Check that the script is run from the repo root."
+            exit 1
+          fi
+          echo "$manifests" | xargs check-jsonschema --schemafile .github/schemas/plugin-manifest.schema.json
+      - name: Validate marketplace registry
+        if: steps.filter.outputs.has_plugin_changes == 'true'
+        run: python .github/scripts/validate-marketplace.py
diff --git a/.yamllint.yml b/.yamllint.yml
new file mode 100644
index 0000000..3312f4f
--- /dev/null
+++ b/.yamllint.yml
@@ -0,0 +1,7 @@
+extends: default
+rules:
+  line-length: disable
+  document-start: disable
+  truthy: disable
+  comments-indentation: disable
+  trailing-spaces: disable