diff --git a/SKILL.md b/SKILL.md
index af35b6c..85a37bc 100644
--- a/SKILL.md
+++ b/SKILL.md
@@ -1,6 +1,6 @@
 ---
 name: isogram
-description: Build animated isometric "how it works" diagrams for web pages: a small physical machine whose motion explains a product feature (calls routed, jobs queued, data synced), with step captions and a live readout. One scene renders in several looks (glow hairline, clean vector, 2:1 pixel art, blueprint; light and dark) and exports as a drop-in <iso-gram> web component (HTML+CSS+JS), a self-contained embed snippet, GIF, PNG, SVG, WebM and a step sheet. Use for feature explainers, landing-page or docs illustrations, onboarding visuals, isometric animated diagrams, pixel-art or vector isometric illustrations, and "iso-glow"/"anatomy"-style figures meant to be embedded.
+description: Build animated isometric "how it works" diagrams for web pages: a small physical machine whose motion explains a product feature (calls routed, jobs queued, data synced), with step captions and a live readout. One scene renders in several looks (glow hairline, clean vector, 2:1 pixel art, blueprint; light and dark) and exports as a drop-in iso-gram web component (HTML+CSS+JS), a self-contained embed snippet, GIF, PNG, SVG, WebM and a step sheet. Use for feature explainers, landing-page or docs illustrations, onboarding visuals, isometric animated diagrams, pixel-art or vector isometric illustrations, and "iso-glow"/"anatomy"-style figures meant to be embedded.
 ---
 
 # isogram
diff --git a/test/skill.test.mjs b/test/skill.test.mjs
index 3af3b0f..2a60788 100644
--- a/test/skill.test.mjs
+++ b/test/skill.test.mjs
@@ -15,6 +15,10 @@ test('SKILL.md has the frontmatter Claude needs', () => {
   const name = m[1].match(/^name: (.+)$/m)?.[1], desc = m[1].match(/^description: (.+)$/m)?.[1]
   assert.equal(name, 'isogram')
   assert.ok(desc && desc.length <= 1024, `description present and ≤ 1024 chars (is ${desc?.length})`)
+  // Claude's skill upload rejects angle brackets in the frontmatter ("description cannot contain XML"),
+  // so write the element as plain iso-gram here; the body of SKILL.md can still say <iso-gram>.
+  for (const [k, v] of Object.entries({ name, description: desc }))
+    assert.doesNotMatch(v, /[<>]/, `${k} must not contain < or > (the skill validator reads them as XML tags)`)
 })
 
 test('every file SKILL.md points to exists', () => {