diff --git a/model/openai.go b/model/openai.go
index fc09bc1..121d9ae 100644
--- a/model/openai.go
+++ b/model/openai.go
@@ -128,26 +128,30 @@ func (opai *OpenAI) System(prompt string) Protocol {
 	return opai
 }
 
-func (opai *OpenAI) User(prompt ...Content) Protocol {
-	raw, err := json.Marshal(&prompt)
+func (opai *OpenAI) normal(role string, prompt ...Content) Protocol {
+	var (
+		raw json.RawMessage
+		err error
+	)
+	if len(prompt) == 1 && prompt[0].Type == ContentTypeText {
+		raw, err = json.Marshal(&prompt[0].Text)
+	} else {
+		raw, err = json.Marshal(&prompt)
+	}
 	if err != nil {
 		panic(err)
 	}
 	opai.Messages = append(opai.Messages, OpenAIMessage{
-		Role:    "user",
+		Role:    role,
 		Content: raw,
 	})
 	return opai
 }
 
-func (opai *OpenAI) Assistant(prompt ...Content) Protocol {
-	raw, err := json.Marshal(&prompt)
-	if err != nil {
-		panic(err)
-	}
-	opai.Messages = append(opai.Messages, OpenAIMessage{
-		Role:    "assistant",
-		Content: raw,
-	})
-	return opai
+func (opai *OpenAI) User(prompt ...Content) Protocol {
+	return opai.normal("user", prompt...)
+}
+
+func (opai *OpenAI) Assistant(prompt ...Content) Protocol {
+	return opai.normal("assistant", prompt...)
 }