diff --git a/go/model.go b/go/model.go
index 6a5b794..62b06b4 100644
--- a/go/model.go
+++ b/go/model.go
@@ -96,7 +96,7 @@ type Item struct {
 	ID             string  `json:"id"`
 	ModelID        string  `json:"modelId"`
 	Fields         []Field `json:"fields"`
-	MetadataFields []Field `json:"metadataFields"`
+	MetadataFields []Field `json:"metadataFields,omitempty"`
 }
 
 func (i *Item) Clone() *Item {
@@ -118,6 +118,14 @@ func (i Item) Field(id string) *Field {
 	return nil
 }
 
+func (i Item) MetadataField(id string) *Field {
+	f, ok := lo.Find(i.MetadataFields, func(f Field) bool { return f.ID == id })
+	if ok {
+		return &f
+	}
+	return nil
+}
+
 func (i Item) FieldByKey(key string) *Field {
 	f, ok := lo.Find(i.Fields, func(f Field) bool { return f.Key == key })
 	if ok {
@@ -126,6 +134,14 @@ func (i Item) FieldByKey(key string) *Field {
 	return nil
 }
 
+func (i Item) MetadataFieldByKey(key string) *Field {
+	f, ok := lo.Find(i.MetadataFields, func(f Field) bool { return f.Key == key })
+	if ok {
+		return &f
+	}
+	return nil
+}
+
 func (d Item) Unmarshal(i any) {
 	if i == nil {
 		return
@@ -146,11 +162,13 @@ func (d Item) Unmarshal(i any) {
 	for i := 0; i < t.NumField(); i++ {
 		f := t.Field(i)
 		tag := f.Tag.Get(tag)
-		key, _, _ := strings.Cut(tag, ",")
+		key, opts, _ := strings.Cut(tag, ",")
 		if key == "" || key == "-" {
 			continue
 		}
 
+		isMetadata := strings.Contains(opts, ",metadata")
+
 		vf := v.FieldByName(f.Name)
 		if !vf.CanSet() {
 			continue
@@ -163,7 +181,14 @@ func (d Item) Unmarshal(i any) {
 			continue
 		}
 
-		if itf := d.FieldByKey(key); itf != nil {
+		var itf *Field
+		if isMetadata {
+			itf = d.MetadataFieldByKey(key)
+		} else {
+			itf = d.FieldByKey(key)
+		}
+
+		if itf != nil {
 			if f.Type.Kind() == reflect.String {
 				if itfv := itf.ValueString(); itfv != nil {
 					vf.SetString(*itfv)
@@ -210,11 +235,14 @@ func Marshal(i any, item *Item) {
 	for i := 0; i < t.NumField(); i++ {
 		f := t.Field(i)
 		tag := f.Tag.Get(tag)
-		key, ty, _ := strings.Cut(tag, ",")
+		key, opts, _ := strings.Cut(tag, ",")
 		if key == "" || key == "-" {
 			continue
 		}
 
+		isMetadata := strings.Contains(opts, ",metadata")
+		ty, _, _ := strings.Cut(opts, ",")
+
 		vf := v.FieldByName(f.Name)
 		if key == "id" {
 			ni.ID, _ = vf.Interface().(string)
@@ -239,11 +267,17 @@ func Marshal(i any, item *Item) {
 		}
 
 		if i != nil {
-			ni.Fields = append(ni.Fields, Field{
+			f := Field{
 				Key:   key,
 				Type:  ty,
 				Value: i,
-			})
+			}
+
+			if isMetadata {
+				ni.MetadataFields = append(ni.MetadataFields, f)
+			} else {
+				ni.Fields = append(ni.Fields, f)
+			}
 		}
 	}
 
diff --git a/go/model_test.go b/go/model_test.go
index ff67835..b5c1e62 100644
--- a/go/model_test.go
+++ b/go/model_test.go
@@ -16,6 +16,7 @@ func TestItem_Unmarshal(t *testing.T) {
 		BBB []string       `cms:"bbb"`
 		CCC []str          `cms:"ccc"`
 		DDD map[string]any `cms:"ddd"`
+		EEE string         `cms:"eee,,metadata"`
 	}
 	s := S{}
 
@@ -27,6 +28,9 @@ func TestItem_Unmarshal(t *testing.T) {
 			{Key: "ccc", Value: []string{"a", "b"}},
 			{Key: "ddd", Value: map[string]any{"a": "b"}},
 		},
+		MetadataFields: []Field{
+			{Key: "eee", Value: "xxx"},
+		},
 	}.Unmarshal(&s)
 	assert.Equal(t, S{
 		ID:  "xxx",
@@ -34,6 +38,7 @@ func TestItem_Unmarshal(t *testing.T) {
 		BBB: []string{"ccc", "bbb"},
 		CCC: []str{"a", "b"},
 		DDD: map[string]any{"a": "b"},
+		EEE: "xxx",
 	}, s)
 
 	// no panic
@@ -51,6 +56,7 @@ func TestMarshal(t *testing.T) {
 		CCC str      `cms:"ccc"`
 		DDD []str    `cms:"ddd"`
 		EEE string   `cms:"eee,text"`
+		FFF string   `cms:"fff,text,metadata"`
 	}
 	s := S{
 		ID:  "xxx",
@@ -58,6 +64,7 @@ func TestMarshal(t *testing.T) {
 		BBB: []string{"ccc", "bbb"},
 		CCC: str("x"),
 		DDD: []str{"1", "2"},
+		FFF: "fff",
 	}
 	i := &Item{
 		ID: "xxx",
@@ -68,6 +75,9 @@ func TestMarshal(t *testing.T) {
 			{Key: "ddd", Type: "", Value: []string{"1", "2"}},
 			// no field for eee
 		},
+		MetadataFields: []Field{
+			{Key: "fff", Type: "text", Value: "fff"},
+		},
 	}
 
 	item := &Item{}
@@ -102,6 +112,23 @@ func TestItem_Field(t *testing.T) {
 	}.Field("ccc"))
 }
 
+func TestItem_MetadataField(t *testing.T) {
+	assert.Equal(t, &Field{
+		ID: "bbb", Value: "ccc", Type: "string",
+	}, Item{
+		MetadataFields: []Field{
+			{ID: "aaa", Value: "bbb", Type: "string"},
+			{ID: "bbb", Value: "ccc", Type: "string"},
+		},
+	}.MetadataField("bbb"))
+	assert.Nil(t, Item{
+		MetadataFields: []Field{
+			{ID: "aaa", Key: "bbb", Type: "string"},
+			{ID: "bbb", Key: "ccc", Type: "string"},
+		},
+	}.MetadataField("ccc"))
+}
+
 func TestItem_FieldByKey(t *testing.T) {
 	assert.Equal(t, &Field{
 		ID: "bbb", Key: "ccc", Type: "string",
@@ -119,6 +146,23 @@ func TestItem_FieldByKey(t *testing.T) {
 	}.FieldByKey("bbb"))
 }
 
+func TestItem_MetadataFieldByKey(t *testing.T) {
+	assert.Equal(t, &Field{
+		ID: "bbb", Key: "ccc", Type: "string",
+	}, Item{
+		MetadataFields: []Field{
+			{ID: "aaa", Key: "bbb", Type: "string"},
+			{ID: "bbb", Key: "ccc", Type: "string"},
+		},
+	}.MetadataFieldByKey("ccc"))
+	assert.Nil(t, Item{
+		MetadataFields: []Field{
+			{ID: "aaa", Key: "aaa", Type: "string"},
+			{ID: "bbb", Key: "ccc", Type: "string"},
+		},
+	}.MetadataFieldByKey("bbb"))
+}
+
 func TestField_ValueString(t *testing.T) {
 	assert.Equal(t, lo.ToPtr("ccc"), (&Field{
 		Value: "ccc",