diff --git a/skill/skill.go b/skill/skill.go
index 7d48cfc..d55663e 100644
--- a/skill/skill.go
+++ b/skill/skill.go
@@ -16,12 +16,12 @@ var _ yaml.Unmarshaler = (*AllowedTools)(nil)
 
 // Frontmatter represents the parsed YAML frontmatter of a SKILL.md file.
 type Frontmatter struct {
-	Name          string            `yaml:"name"`
-	Description   string            `yaml:"description"`
-	License       string            `yaml:"license"`
-	Compatibility string            `yaml:"compatibility"`
-	Metadata      map[string]string `yaml:"metadata"`
-	AllowedTools  AllowedTools      `yaml:"allowed-tools"`
+	Name          string         `yaml:"name"`
+	Description   string         `yaml:"description"`
+	License       string         `yaml:"license"`
+	Compatibility string         `yaml:"compatibility"`
+	Metadata      map[string]any `yaml:"metadata"`
+	AllowedTools  AllowedTools   `yaml:"allowed-tools"`
 }
 
 // AllowedTools handles the type ambiguity in the allowed-tools field.
diff --git a/skill/skill_test.go b/skill/skill_test.go
index ad7ef16..972985e 100644
--- a/skill/skill_test.go
+++ b/skill/skill_test.go
@@ -237,6 +237,28 @@ func TestLoad(t *testing.T) {
 		}
 	})
 
+	t.Run("metadata with sequence value parses without error", func(t *testing.T) {
+		dir := t.TempDir()
+		content := "---\nname: test\ndescription: desc\nmetadata:\n  author: alice\n  tags: [foo, bar, baz]\n---\nBody\n"
+		if err := os.WriteFile(filepath.Join(dir, "SKILL.md"), []byte(content), 0o644); err != nil {
+			t.Fatal(err)
+		}
+		s, err := Load(dir)
+		if err != nil {
+			t.Fatalf("unexpected error: %v", err)
+		}
+		if s.Frontmatter.Metadata["author"] != "alice" {
+			t.Errorf("metadata[author] = %v, want %q", s.Frontmatter.Metadata["author"], "alice")
+		}
+		tags, ok := s.Frontmatter.Metadata["tags"].([]any)
+		if !ok {
+			t.Fatalf("metadata[tags] = %T, want []any", s.Frontmatter.Metadata["tags"])
+		}
+		if len(tags) != 3 {
+			t.Errorf("metadata[tags] len = %d, want 3", len(tags))
+		}
+	})
+
 	t.Run("metadata parsing", func(t *testing.T) {
 		dir := t.TempDir()
 		content := "---\nname: test\ndescription: desc\nmetadata:\n  author: alice\n  version: \"1.0\"\n---\nBody\n"
@@ -248,10 +270,10 @@ func TestLoad(t *testing.T) {
 			t.Fatalf("unexpected error: %v", err)
 		}
 		if s.Frontmatter.Metadata["author"] != "alice" {
-			t.Errorf("metadata[author] = %q, want %q", s.Frontmatter.Metadata["author"], "alice")
+			t.Errorf("metadata[author] = %v, want %q", s.Frontmatter.Metadata["author"], "alice")
 		}
 		if s.Frontmatter.Metadata["version"] != "1.0" {
-			t.Errorf("metadata[version] = %q, want %q", s.Frontmatter.Metadata["version"], "1.0")
+			t.Errorf("metadata[version] = %v, want %q", s.Frontmatter.Metadata["version"], "1.0")
 		}
 	})
 }
diff --git a/structure/frontmatter.go b/structure/frontmatter.go
index 83ffa05..08a4e06 100644
--- a/structure/frontmatter.go
+++ b/structure/frontmatter.go
@@ -68,20 +68,23 @@ func CheckFrontmatter(s *skill.Skill, opts Options) []types.Result {
 
 	// Check optional metadata
 	if s.RawFrontmatter["metadata"] != nil {
-		// Verify it's a map[string]string
+		// Verify it's a map whose values are non-nil, non-empty
 		if m, ok := s.RawFrontmatter["metadata"].(map[string]any); ok {
-			allStrings := true
+			valid := true
 			for k, v := range m {
-				if _, ok := v.(string); !ok {
-					results = append(results, ctx.Errorf("metadata[%q] value must be a string", k))
-					allStrings = false
+				if v == nil {
+					results = append(results, ctx.Errorf("metadata[%q] value must not be null", k))
+					valid = false
+				} else if s, ok := v.(string); ok && s == "" {
+					results = append(results, ctx.Errorf("metadata[%q] value must not be empty", k))
+					valid = false
 				}
 			}
-			if allStrings {
+			if valid {
 				results = append(results, ctx.Passf("metadata: (%d entries)", len(m)))
 			}
 		} else {
-			results = append(results, ctx.Error("metadata must be a map of string keys to string values"))
+			results = append(results, ctx.Error("metadata must be a map"))
 		}
 	}
 
diff --git a/structure/frontmatter_test.go b/structure/frontmatter_test.go
index 6b96866..d9e6903 100644
--- a/structure/frontmatter_test.go
+++ b/structure/frontmatter_test.go
@@ -373,20 +373,56 @@ func TestCheckFrontmatter_Metadata(t *testing.T) {
 		requireResultContaining(t, results, types.Pass, "metadata: (2 entries)")
 	})
 
-	t.Run("metadata with non-string value", func(t *testing.T) {
+	t.Run("metadata with integer value", func(t *testing.T) {
 		s := makeSkill("/tmp/my-skill", "my-skill", "desc")
 		s.RawFrontmatter["metadata"] = map[string]any{
 			"count": 42,
 		}
 		results := CheckFrontmatter(s, Options{})
-		requireResultContaining(t, results, types.Error, "metadata[\"count\"] value must be a string")
+		requireResultContaining(t, results, types.Pass, "metadata: (1 entries)")
+	})
+
+	t.Run("metadata with float value", func(t *testing.T) {
+		s := makeSkill("/tmp/my-skill", "my-skill", "desc")
+		s.RawFrontmatter["metadata"] = map[string]any{
+			"score": 3.14,
+		}
+		results := CheckFrontmatter(s, Options{})
+		requireResultContaining(t, results, types.Pass, "metadata: (1 entries)")
+	})
+
+	t.Run("metadata with sequence value", func(t *testing.T) {
+		s := makeSkill("/tmp/my-skill", "my-skill", "desc")
+		s.RawFrontmatter["metadata"] = map[string]any{
+			"tags": []any{"foo", "bar"},
+		}
+		results := CheckFrontmatter(s, Options{})
+		requireResultContaining(t, results, types.Pass, "metadata: (1 entries)")
+	})
+
+	t.Run("metadata with null value", func(t *testing.T) {
+		s := makeSkill("/tmp/my-skill", "my-skill", "desc")
+		s.RawFrontmatter["metadata"] = map[string]any{
+			"key": nil,
+		}
+		results := CheckFrontmatter(s, Options{})
+		requireResultContaining(t, results, types.Error, "metadata[\"key\"] value must not be null")
+	})
+
+	t.Run("metadata with empty string value", func(t *testing.T) {
+		s := makeSkill("/tmp/my-skill", "my-skill", "desc")
+		s.RawFrontmatter["metadata"] = map[string]any{
+			"key": "",
+		}
+		results := CheckFrontmatter(s, Options{})
+		requireResultContaining(t, results, types.Error, "metadata[\"key\"] value must not be empty")
 	})
 
 	t.Run("metadata not a map", func(t *testing.T) {
 		s := makeSkill("/tmp/my-skill", "my-skill", "desc")
 		s.RawFrontmatter["metadata"] = "not a map"
 		results := CheckFrontmatter(s, Options{})
-		requireResult(t, results, types.Error, "metadata must be a map of string keys to string values")
+		requireResult(t, results, types.Error, "metadata must be a map")
 	})
 }