diff --git a/tools/README.md b/tools/README.md
index edf3c13d..19e8c64b 100644
--- a/tools/README.md
+++ b/tools/README.md
@@ -20,7 +20,7 @@ python tools/validate-skill.py --all
 - Valid YAML frontmatter (between `---` markers)
 - Required fields present: `name`, `description`, `domain`, `subdomain`, `tags`
 - Name is kebab-case, 1–64 characters
-- Description is 20–500 characters
+- Description is at least 50 characters (no upper limit; multi-line folded scalars are valid)
 - Domain is `cybersecurity`
 - Subdomain is from the allowed list
 - Tags is a list with at least 2 items
diff --git a/tools/validate-skill.py b/tools/validate-skill.py
index 9411b9a3..9932abc8 100755
--- a/tools/validate-skill.py
+++ b/tools/validate-skill.py
@@ -205,7 +205,9 @@ def validate_skill(skill_dir):
 
     # Validate description.
     desc = fm.get("description", "")
-    if isinstance(desc, str):
+    if isinstance(desc, list):
+        errors.append("Description must be a string value, not a list")
+    elif isinstance(desc, str):
         if len(desc) < DESCRIPTION_MIN_CHARS:
             errors.append(
                 f"Description too short ({len(desc)} chars, min {DESCRIPTION_MIN_CHARS})"
@@ -251,6 +253,9 @@ def main():
 
     if sys.argv[1] == "--all":
         skill_dirs = sorted(glob.glob("skills/*/"))
+        if not skill_dirs:
+            print("ERROR: No skill directories found. Run from the repository root.")
+            sys.exit(1)
     else:
         skill_dirs = [sys.argv[1].rstrip("/") + "/"]