diff --git a/src/open_prompt_extension.cpp b/src/open_prompt_extension.cpp
index cf57b5a..e6625ba 100644
--- a/src/open_prompt_extension.cpp
+++ b/src/open_prompt_extension.cpp
@@ -24,19 +24,23 @@ namespace duckdb {
     struct OpenPromptData: FunctionData {
         idx_t model_idx;
         idx_t json_schema_idx;
+        idx_t json_system_prompt_idx;
         unique_ptr<FunctionData> Copy() const {
             auto res = make_uniq<OpenPromptData>();
             res->model_idx = model_idx;
             res->json_schema_idx = json_schema_idx;
+            res->json_system_prompt_idx = json_system_prompt_idx;
             return res;
         };
         bool Equals(const FunctionData &other) const {
             return model_idx == other.Cast<OpenPromptData>().model_idx &&
-                json_schema_idx == other.Cast<OpenPromptData>().json_schema_idx;
+                json_schema_idx == other.Cast<OpenPromptData>().json_schema_idx &&
+                json_system_prompt_idx==other.Cast<OpenPromptData>().json_system_prompt_idx;
         };
         OpenPromptData() {
             model_idx = 0;
             json_schema_idx = 0;
+            json_system_prompt_idx = 0;
         }
     };
 
@@ -49,6 +53,8 @@ namespace duckdb {
                 res->model_idx = i;
             } else if (argument->alias == "json_schema") {
                 res->json_schema_idx = i;
+            } else if (argument->alias == "system_prompt") {
+                res->json_system_prompt_idx = i;
             }
         }
         return std::move(res);
@@ -182,6 +188,7 @@ static void OpenPromptRequestFunction(DataChunk &args, ExpressionState &state, V
             std::string api_token = GetConfigValue(context, "openprompt_api_token", "");
             std::string model_name = GetConfigValue(context, "openprompt_model_name", "qwen2.5:0.5b");
             std::string json_schema;
+            std::string system_prompt;
 
             if (info.model_idx != 0) {
                 model_name = args.data[info.model_idx].GetValue(0).ToString();
@@ -189,19 +196,57 @@ static void OpenPromptRequestFunction(DataChunk &args, ExpressionState &state, V
             if (info.json_schema_idx != 0) {
                 json_schema = args.data[info.json_schema_idx].GetValue(0).ToString();
             }
+            if (info.json_system_prompt_idx != 0) {
+                system_prompt = args.data[info.json_system_prompt_idx].GetValue(0).ToString();
+            }
 
-            std::string request_body = "{";
-            request_body += "\"model\":\"" + model_name + "\",";
+            unique_ptr<duckdb_yyjson::yyjson_mut_doc, void (*)(duckdb_yyjson::yyjson_mut_doc*)> doc(
+                    duckdb_yyjson::yyjson_mut_doc_new(nullptr), &duckdb_yyjson::yyjson_mut_doc_free);
+            auto obj = duckdb_yyjson::yyjson_mut_obj(doc.get());
+            duckdb_yyjson::yyjson_mut_doc_set_root(doc.get(), obj);
+            duckdb_yyjson::yyjson_mut_obj_add(obj,
+                duckdb_yyjson::yyjson_mut_str(doc.get(), "model"),
+                duckdb_yyjson::yyjson_mut_str(doc.get(), model_name.c_str())
+                );
             if (!json_schema.empty()) {
-                request_body += "\"response_format\":{\"type\":\"json_object\", \"schema\":";
-                request_body += json_schema;
-                request_body += "},";
+                auto response_format = duckdb_yyjson::yyjson_mut_obj(doc.get());
+                duckdb_yyjson::yyjson_mut_obj_add(response_format,
+                    duckdb_yyjson::yyjson_mut_str(doc.get(), "type"),
+                    duckdb_yyjson::yyjson_mut_str(doc.get(), "json_object"));
+                auto yyschema = duckdb_yyjson::yyjson_mut_raw(doc.get(), json_schema.c_str());
+                duckdb_yyjson::yyjson_mut_obj_add(response_format,
+                    duckdb_yyjson::yyjson_mut_str(doc.get(), "schema"),
+                    yyschema);
+                duckdb_yyjson::yyjson_mut_obj_add(obj,
+                    duckdb_yyjson::yyjson_mut_str(doc.get(),"response_format"),
+                    response_format);
             }
-            request_body += "\"messages\":[";
-            request_body += "{\"role\":\"system\",\"content\":\"You are a helpful assistant.\"},";
-            request_body += "{\"role\":\"user\",\"content\":\"" + user_prompt.GetString() + "\"}";
-            request_body += "]}";
-
+            auto messages = duckdb_yyjson::yyjson_mut_arr(doc.get());
+            string str_messages[2][2] = {
+                {"system", system_prompt},
+                {"user", user_prompt.GetString()}
+            };
+            for (auto message : str_messages) {
+                if (message[1].empty()) {
+                    continue;
+                }
+                auto yymessage = duckdb_yyjson::yyjson_mut_arr_add_obj(doc.get(),messages);
+                duckdb_yyjson::yyjson_mut_obj_add(yymessage,
+                    duckdb_yyjson::yyjson_mut_str(doc.get(), "role"),
+                    duckdb_yyjson::yyjson_mut_str(doc.get(), message[0].c_str()));
+                duckdb_yyjson::yyjson_mut_obj_add(yymessage,
+                    duckdb_yyjson::yyjson_mut_str(doc.get(), "content"),
+                    duckdb_yyjson::yyjson_mut_str(doc.get(), message[1].c_str()));
+            }
+            duckdb_yyjson::yyjson_mut_obj_add(obj, duckdb_yyjson::yyjson_mut_str(doc.get(), "messages"),
+                messages);
+            duckdb_yyjson::yyjson_write_err err;
+            auto request_body = duckdb_yyjson::yyjson_mut_write_opts(doc.get(), 0, nullptr, nullptr, &err);
+            if (request_body == nullptr) {
+                throw std::runtime_error(err.msg);
+            }
+            string str_request_body(request_body);
+            free(request_body);
 
             try {
                 auto client_and_path = SetupHttpClient(api_url);
@@ -214,7 +259,7 @@ static void OpenPromptRequestFunction(DataChunk &args, ExpressionState &state, V
                     headers.emplace("Authorization", "Bearer " + api_token);
                 }
 
-                auto res = client.Post(path.c_str(), headers, request_body, "application/json");
+                auto res = client.Post(path.c_str(), headers, str_request_body, "application/json");
                 
                 if (!res) {
                     HandleHttpError(res, "POST");
@@ -286,10 +331,14 @@ static void LoadInternal(DatabaseInstance &instance) {
     open_prompt.AddFunction(ScalarFunction(
         {LogicalType::VARCHAR, LogicalType::VARCHAR}, LogicalType::VARCHAR, OpenPromptRequestFunction,
         OpenPromptBind));
-        open_prompt.AddFunction(ScalarFunction(
+    open_prompt.AddFunction(ScalarFunction(
         {LogicalType::VARCHAR, LogicalType::VARCHAR, LogicalType::VARCHAR},
         LogicalType::VARCHAR, OpenPromptRequestFunction,
         OpenPromptBind));
+    open_prompt.AddFunction(ScalarFunction(
+        {LogicalType::VARCHAR, LogicalType::VARCHAR, LogicalType::VARCHAR, LogicalType::VARCHAR},
+        LogicalType::VARCHAR, OpenPromptRequestFunction,
+        OpenPromptBind));
     
     ExtensionUtil::RegisterFunction(instance, open_prompt);