diff --git a/assistant.go b/assistant.go
index d75eebef..de49be68 100644
--- a/assistant.go
+++ b/assistant.go
@@ -10,46 +10,43 @@ import (
 const (
 	assistantsSuffix      = "/assistants"
 	assistantsFilesSuffix = "/files"
+	openaiAssistantsV1    = "assistants=v1"
 )
 
 type Assistant struct {
-	ID           string  `json:"id"`
-	Object       string  `json:"object"`
-	CreatedAt    int64   `json:"created_at"`
-	Name         *string `json:"name,omitempty"`
-	Description  *string `json:"description,omitempty"`
-	Model        string  `json:"model"`
-	Instructions *string `json:"instructions,omitempty"`
-	Tools        []any   `json:"tools,omitempty"`
+	ID           string          `json:"id"`
+	Object       string          `json:"object"`
+	CreatedAt    int64           `json:"created_at"`
+	Name         *string         `json:"name,omitempty"`
+	Description  *string         `json:"description,omitempty"`
+	Model        string          `json:"model"`
+	Instructions *string         `json:"instructions,omitempty"`
+	Tools        []AssistantTool `json:"tools,omitempty"`
 
 	httpHeader
 }
 
-type AssistantTool struct {
-	Type string `json:"type"`
-}
-
-type AssistantToolCodeInterpreter struct {
-	AssistantTool
-}
+type AssistantToolType string
 
-type AssistantToolRetrieval struct {
-	AssistantTool
-}
+const (
+	AssistantToolTypeCodeInterpreter AssistantToolType = "code_interpreter"
+	AssistantToolTypeRetrieval       AssistantToolType = "retrieval"
+	AssistantToolTypeFunction        AssistantToolType = "function"
+)
 
-type AssistantToolFunction struct {
-	AssistantTool
-	Function FunctionDefinition `json:"function"`
+type AssistantTool struct {
+	Type     AssistantToolType   `json:"type"`
+	Function *FunctionDefinition `json:"function,omitempty"`
 }
 
 type AssistantRequest struct {
-	Model        string         `json:"model"`
-	Name         *string        `json:"name,omitempty"`
-	Description  *string        `json:"description,omitempty"`
-	Instructions *string        `json:"instructions,omitempty"`
-	Tools        []any          `json:"tools,omitempty"`
-	FileIDs      []string       `json:"file_ids,omitempty"`
-	Metadata     map[string]any `json:"metadata,omitempty"`
+	Model        string          `json:"model"`
+	Name         *string         `json:"name,omitempty"`
+	Description  *string         `json:"description,omitempty"`
+	Instructions *string         `json:"instructions,omitempty"`
+	Tools        []AssistantTool `json:"tools,omitempty"`
+	FileIDs      []string        `json:"file_ids,omitempty"`
+	Metadata     map[string]any  `json:"metadata,omitempty"`
 }
 
 // AssistantsList is a list of assistants.
@@ -59,6 +56,14 @@ type AssistantsList struct {
 	httpHeader
 }
 
+type AssistantDeleteResponse struct {
+	ID      string `json:"id"`
+	Object  string `json:"object"`
+	Deleted bool   `json:"deleted"`
+
+	httpHeader
+}
+
 type AssistantFile struct {
 	ID          string `json:"id"`
 	Object      string `json:"object"`
@@ -80,7 +85,8 @@ type AssistantFilesList struct {
 
 // CreateAssistant creates a new assistant.
 func (c *Client) CreateAssistant(ctx context.Context, request AssistantRequest) (response Assistant, err error) {
-	req, err := c.newRequest(ctx, http.MethodPost, c.fullURL(assistantsSuffix), withBody(request))
+	req, err := c.newRequest(ctx, http.MethodPost, c.fullURL(assistantsSuffix), withBody(request),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
@@ -95,7 +101,8 @@ func (c *Client) RetrieveAssistant(
 	assistantID string,
 ) (response Assistant, err error) {
 	urlSuffix := fmt.Sprintf("%s/%s", assistantsSuffix, assistantID)
-	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix))
+	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
@@ -111,7 +118,8 @@ func (c *Client) ModifyAssistant(
 	request AssistantRequest,
 ) (response Assistant, err error) {
 	urlSuffix := fmt.Sprintf("%s/%s", assistantsSuffix, assistantID)
-	req, err := c.newRequest(ctx, http.MethodPost, c.fullURL(urlSuffix), withBody(request))
+	req, err := c.newRequest(ctx, http.MethodPost, c.fullURL(urlSuffix), withBody(request),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
@@ -124,9 +132,10 @@ func (c *Client) ModifyAssistant(
 func (c *Client) DeleteAssistant(
 	ctx context.Context,
 	assistantID string,
-) (response Assistant, err error) {
+) (response AssistantDeleteResponse, err error) {
 	urlSuffix := fmt.Sprintf("%s/%s", assistantsSuffix, assistantID)
-	req, err := c.newRequest(ctx, http.MethodDelete, c.fullURL(urlSuffix))
+	req, err := c.newRequest(ctx, http.MethodDelete, c.fullURL(urlSuffix),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
@@ -163,7 +172,8 @@ func (c *Client) ListAssistants(
 	}
 
 	urlSuffix := fmt.Sprintf("%s%s", assistantsSuffix, encodedValues)
-	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix))
+	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
@@ -180,7 +190,8 @@ func (c *Client) CreateAssistantFile(
 ) (response AssistantFile, err error) {
 	urlSuffix := fmt.Sprintf("%s/%s%s", assistantsSuffix, assistantID, assistantsFilesSuffix)
 	req, err := c.newRequest(ctx, http.MethodPost, c.fullURL(urlSuffix),
-		withBody(request))
+		withBody(request),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
@@ -196,7 +207,8 @@ func (c *Client) RetrieveAssistantFile(
 	fileID string,
 ) (response AssistantFile, err error) {
 	urlSuffix := fmt.Sprintf("%s/%s%s/%s", assistantsSuffix, assistantID, assistantsFilesSuffix, fileID)
-	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix))
+	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
@@ -212,7 +224,8 @@ func (c *Client) DeleteAssistantFile(
 	fileID string,
 ) (err error) {
 	urlSuffix := fmt.Sprintf("%s/%s%s/%s", assistantsSuffix, assistantID, assistantsFilesSuffix, fileID)
-	req, err := c.newRequest(ctx, http.MethodDelete, c.fullURL(urlSuffix))
+	req, err := c.newRequest(ctx, http.MethodDelete, c.fullURL(urlSuffix),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
@@ -250,7 +263,8 @@ func (c *Client) ListAssistantFiles(
 	}
 
 	urlSuffix := fmt.Sprintf("%s/%s%s%s", assistantsSuffix, assistantID, assistantsFilesSuffix, encodedValues)
-	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix))
+	req, err := c.newRequest(ctx, http.MethodGet, c.fullURL(urlSuffix),
+		withBetaAssistantV1())
 	if err != nil {
 		return
 	}
diff --git a/client.go b/client.go
index 65ece812..056226c6 100644
--- a/client.go
+++ b/client.go
@@ -83,6 +83,12 @@ func withContentType(contentType string) requestOption {
 	}
 }
 
+func withBetaAssistantV1() requestOption {
+	return func(args *requestOptions) {
+		args.header.Set("OpenAI-Beta", "assistants=v1")
+	}
+}
+
 func (c *Client) newRequest(ctx context.Context, method, url string, setters ...requestOption) (*http.Request, error) {
 	// Default Options
 	args := &requestOptions{