diff --git a/.github/workflows/validate-plugins.yml b/.github/workflows/validate-plugins.yml
index 03e8e1928..89cc7b5dc 100644
--- a/.github/workflows/validate-plugins.yml
+++ b/.github/workflows/validate-plugins.yml
@@ -5,7 +5,9 @@ on:
     paths:
       - ".cursor-plugin/marketplace.json"
       - "**/plugin.json"
+      - "**/SKILL.md"
       - "schemas/**"
+      - "scripts/**"
 
 jobs:
   validate:
@@ -18,7 +20,7 @@ jobs:
           node-version: 20
 
       - name: Install dependencies
-        run: npm install --no-save ajv ajv-formats
+        run: npm install --no-save ajv ajv-formats yaml
 
       - name: Validate plugin definitions
         run: node scripts/validate-plugins.mjs
diff --git a/agent-compatibility/skills/check-agent-compatibility/SKILL.md b/agent-compatibility/skills/check-agent-compatibility/SKILL.md
index 6d88d4a5f..40e4a0446 100644
--- a/agent-compatibility/skills/check-agent-compatibility/SKILL.md
+++ b/agent-compatibility/skills/check-agent-compatibility/SKILL.md
@@ -1,6 +1,6 @@
 ---
 name: check-agent-compatibility
-description: Run the full repository compatibility pass: scanner score, startup path, validation loop, and docs reliability.
+description: "Run the full repository compatibility pass: scanner score, startup path, validation loop, and docs reliability."
 ---
 
 # Check agent compatibility
diff --git a/pstack/skills/make-bot-ui/SKILL.md b/pstack/skills/make-bot-ui/SKILL.md
index 285df7569..446342ca3 100644
--- a/pstack/skills/make-bot-ui/SKILL.md
+++ b/pstack/skills/make-bot-ui/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: Make Bot UI
+name: make-bot-ui
 description: >-
   Use when building a custom UI (page, dashboard, buttons) that should wake a
   Grok Bot over a webhook, when the user must provide a webhook sender key, or
diff --git a/pstack/skills/poteto-mode/SKILL.md b/pstack/skills/poteto-mode/SKILL.md
index f8ddcae37..3b4dcbedf 100644
--- a/pstack/skills/poteto-mode/SKILL.md
+++ b/pstack/skills/poteto-mode/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: Poteto Mode
+name: poteto-mode
 description: poteto's agent style for concise, detailed responses, deliberate subagents, unslopped prose, simple code, and verified work. Use for poteto, /poteto-mode, or requests to work in this style.
 disable-model-invocation: true
 mode: true
diff --git a/schemas/skill.schema.json b/schemas/skill.schema.json
new file mode 100644
index 000000000..e4eb1eb1d
--- /dev/null
+++ b/schemas/skill.schema.json
@@ -0,0 +1,22 @@
+{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "$id": "https://cursor.com/schemas/cursor-plugin/skill.json",
+  "title": "Cursor Skill Frontmatter",
+  "description": "Schema for the YAML frontmatter of a SKILL.md — defines a single skill's metadata. Unknown keys are permitted so plugins can add harness-specific options.",
+  "type": "object",
+  "required": ["name", "description"],
+  "additionalProperties": true,
+  "properties": {
+    "name": {
+      "type": "string",
+      "minLength": 1,
+      "pattern": "^[a-z0-9]([a-z0-9.-]*[a-z0-9])?$",
+      "description": "Unique skill identifier in kebab-case. Must match the skill's folder name."
+    },
+    "description": {
+      "type": "string",
+      "minLength": 1,
+      "description": "Short description of what the skill does and when to use it."
+    }
+  }
+}
diff --git a/scripts/validate-plugins.mjs b/scripts/validate-plugins.mjs
index 6a7870854..3e5ab70c0 100644
--- a/scripts/validate-plugins.mjs
+++ b/scripts/validate-plugins.mjs
@@ -1,10 +1,11 @@
 #!/usr/bin/env node
 
-import { readFileSync, existsSync } from "fs";
-import { resolve, dirname } from "path";
+import { readFileSync, existsSync, readdirSync } from "fs";
+import { resolve, dirname, basename, relative } from "path";
 import { fileURLToPath } from "url";
 import Ajv from "ajv";
 import addFormats from "ajv-formats";
+import { parse as parseYaml } from "yaml";
 
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const root = resolve(__dirname, "..");
@@ -17,12 +18,14 @@ const marketplaceSchema = loadJSON(
   resolve(root, "schemas/marketplace.schema.json")
 );
 const pluginSchema = loadJSON(resolve(root, "schemas/plugin.schema.json"));
+const skillSchema = loadJSON(resolve(root, "schemas/skill.schema.json"));
 
 const ajv = new Ajv({ allErrors: true });
 addFormats(ajv);
 
 const validateMarketplace = ajv.compile(marketplaceSchema);
 const validatePlugin = ajv.compile(pluginSchema);
+const validateSkill = ajv.compile(skillSchema);
 
 let errors = 0;
 
@@ -92,7 +95,81 @@ for (const entry of marketplace.plugins ?? []) {
   }
 }
 
-// 3. Report results
+// 3. Check every plugin in the repository is registered in the marketplace
+const marketplaceSources = new Set(
+  (marketplace.plugins ?? []).map((entry) => resolve(root, entry.source))
+);
+
+const pluginDirs = [];
+
+(function collectPluginDirs(dir) {
+  for (const entry of readdirSync(dir, { withFileTypes: true })) {
+    if (entry.name === ".git" || entry.name === "node_modules") continue;
+    const full = resolve(dir, entry.name);
+    if (!entry.isDirectory()) continue;
+    if (existsSync(resolve(full, ".cursor-plugin/plugin.json"))) {
+      pluginDirs.push(full);
+    } else {
+      collectPluginDirs(full);
+    }
+  }
+})(root);
+
+for (const pluginDir of pluginDirs) {
+  if (!marketplaceSources.has(pluginDir)) {
+    fail(
+      `${relative(root, pluginDir)}: has a .cursor-plugin/plugin.json but is not listed in .cursor-plugin/marketplace.json`
+    );
+  }
+}
+
+// 4. Validate skill frontmatter
+const skillFiles = [];
+
+(function collectSkillFiles(dir) {
+  for (const entry of readdirSync(dir, { withFileTypes: true })) {
+    if (entry.name === ".git" || entry.name === "node_modules") continue;
+    const full = resolve(dir, entry.name);
+    if (entry.isDirectory()) collectSkillFiles(full);
+    else if (entry.name === "SKILL.md") skillFiles.push(full);
+  }
+})(root);
+
+for (const skillPath of skillFiles.sort()) {
+  const skillRel = relative(root, skillPath);
+  const text = readFileSync(skillPath, "utf-8");
+  const frontmatterMatch = /^---\r?\n([\s\S]*?)\r?\n---(?:\r?\n|$)/.exec(text);
+
+  if (!frontmatterMatch) {
+    fail(`${skillRel}: missing YAML frontmatter (file must start with "---")`);
+    continue;
+  }
+
+  let frontmatter;
+  try {
+    frontmatter = parseYaml(frontmatterMatch[1]) ?? {};
+  } catch (err) {
+    fail(`${skillRel}: frontmatter is not valid YAML (${err.message.split("\n")[0]})`);
+    continue;
+  }
+
+  if (!validateSkill(frontmatter)) {
+    fail(`${skillRel}: frontmatter does not match schemas/skill.schema.json:`);
+    for (const err of validateSkill.errors) {
+      console.error(`  ${err.instancePath || "/"}: ${err.message}`);
+    }
+    continue;
+  }
+
+  const folder = basename(dirname(skillPath));
+  if (frontmatter.name !== folder) {
+    fail(
+      `${skillRel}: frontmatter name "${frontmatter.name}" does not match folder name "${folder}"`
+    );
+  }
+}
+
+// 5. Report results
 if (errors > 0) {
   console.error(`\nValidation failed with ${errors} error(s).`);
   process.exit(1);
diff --git a/third_party/x-money/skills/x-money-guide/SKILL.md b/third_party/x-money/skills/x-money-guide/SKILL.md
index a40a45126..ee8738379 100644
--- a/third_party/x-money/skills/x-money-guide/SKILL.md
+++ b/third_party/x-money/skills/x-money-guide/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: X Money guide
+name: x-money-guide
 description: >-
   Read this before the first X Money action in a session and again on any
   X Money error, refusal, or missing capability. Covers the approval rule for
diff --git a/third_party/x/skills/x-api-mcp-guide/SKILL.md b/third_party/x/skills/x-api-mcp-guide/SKILL.md
index 5bf111d80..43ed1d3de 100644
--- a/third_party/x/skills/x-api-mcp-guide/SKILL.md
+++ b/third_party/x/skills/x-api-mcp-guide/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: X MCP guide
+name: x-api-mcp-guide
 description: >-
   ALWAYS read this when a user connects the X plugin or any X MCP, before using
   any X connection, and again on any X error. Do not call an X tool until this
diff --git a/third_party/x/skills/x-chat/SKILL.md b/third_party/x/skills/x-chat/SKILL.md
index 0d2b97a92..3ae4fb4cd 100644
--- a/third_party/x/skills/x-chat/SKILL.md
+++ b/third_party/x/skills/x-chat/SKILL.md
@@ -1,5 +1,5 @@
 ---
-name: X Chat
+name: x-chat
 description: >-
   Read, summarize, or send encrypted X Chat (XChat) DMs via the X plugin MCP
   plus local chatxdk / xchat_lite.py. Use when the user mentions X Chat, xchat,