diff --git a/model_types.go b/model_types.go
index e0eb956..9a9b34f 100644
--- a/model_types.go
+++ b/model_types.go
@@ -138,10 +138,10 @@ type GetDownloadUriForModelVersionArtifactsResponse struct {
 }
 
 type SearchModelVersionsRequest struct {
-	Filter     string
-	MaxResults int64
-	OrderBy    []string
-	PageToken  string
+	Filter     string   `json:"filter,omitempty"`
+	MaxResults int64    `json:"max_results,omitempty"`
+	OrderBy    []string `json:"order_by,omitempty"`
+	PageToken  string   `json:"page_token,omitempty"`
 }
 
 func (e *SearchModelVersionsRequest) serialize() []byte {
@@ -202,10 +202,10 @@ func (e *TransitionModelVersionStageRequest) serialize() []byte {
 type TransitionModelVersionStageResponse GetModelVersionResponse
 
 type SearchRegisteredModelsRequest struct {
-	Filter     string
-	MaxResults int64
-	OrderBy    []string
-	PageToken  string
+	Filter     string   `json:"filter,omitempty"`
+	MaxResults int64    `json:"max_results,omitempty"`
+	OrderBy    []string `json:"order_by,omitempty"`
+	PageToken  string   `json:"page_token,omitempty"`
 }
 
 func (e *SearchRegisteredModelsRequest) serialize() []byte {