diff --git a/src/v1/api.rs b/src/v1/api.rs
index ce0b1c4..a26ebab 100644
--- a/src/v1/api.rs
+++ b/src/v1/api.rs
@@ -62,6 +62,7 @@ pub struct OpenAIClientBuilder {
     proxy: Option<String>,
     timeout: Option<u64>,
     headers: Option<HeaderMap>,
+    additional_json: Option<Value>,
 }
 
 #[derive(Debug)]
@@ -72,6 +73,7 @@ pub struct OpenAIClient {
     proxy: Option<String>,
     timeout: Option<u64>,
     headers: Option<HeaderMap>,
+    additional_json: Option<Value>,
     pub response_headers: Option<HeaderMap>,
 }
 
@@ -114,6 +116,11 @@ impl OpenAIClientBuilder {
         self
     }
 
+    pub fn with_additional_json(mut self, additional_json: Value) -> Self {
+        self.additional_json = Some(additional_json);
+        self
+    }
+
     pub fn build(self) -> Result<OpenAIClient, Box<dyn Error>> {
         let api_endpoint = self.api_endpoint.unwrap_or_else(|| {
             std::env::var("OPENAI_API_BASE").unwrap_or_else(|_| API_URL_V1.to_owned())
@@ -127,6 +134,7 @@ impl OpenAIClientBuilder {
             timeout: self.timeout,
             headers: self.headers,
             response_headers: None,
+            additional_json: self.additional_json,
         })
     }
 }
@@ -189,6 +197,19 @@ impl OpenAIClient {
         body: &impl serde::ser::Serialize,
     ) -> Result<T, APIError> {
         let request = self.build_request(Method::POST, path).await;
+
+        let request = if let Some(additional_json) = &self.additional_json {
+            let mut body = serde_json::to_value(body).unwrap();
+            if let Value::Object(map) = &mut body {
+                for (key, value) in additional_json.as_object().unwrap() {
+                    map.insert(key.clone(), value.clone());
+                }
+            }
+            request.json(&body)
+        } else {
+            request.json(body)
+        };
+
         let request = request.json(body);
         let response = request.send().await?;
         self.handle_response(response).await