diff --git a/async-openai/src/types/admin/api_keys/api_keys_.rs b/async-openai/src/types/admin/api_keys/api_keys_.rs
index 2eee47be..db6450bb 100644
--- a/async-openai/src/types/admin/api_keys/api_keys_.rs
+++ b/async-openai/src/types/admin/api_keys/api_keys_.rs
@@ -50,9 +50,9 @@ pub struct ApiKeyList {
     /// Indicates if there are more admin API keys available.
     pub has_more: bool,
     /// The ID of the first admin API key in the list.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The ID of the last admin API key in the list.
-    pub last_id: String,
+    pub last_id: Option<String>,
 }
 
 /// Represents the request object for creating an admin API key.
diff --git a/async-openai/src/types/admin/audit_logs/audit_logs_.rs b/async-openai/src/types/admin/audit_logs/audit_logs_.rs
index 1d3b137e..703c33ac 100644
--- a/async-openai/src/types/admin/audit_logs/audit_logs_.rs
+++ b/async-openai/src/types/admin/audit_logs/audit_logs_.rs
@@ -53,9 +53,9 @@ pub struct ListAuditLogsResponse {
     /// A list of `AuditLog` objects.
     pub data: Vec<AuditLog>,
     /// The first `audit_log_id` in the retrieved `list`.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The last `audit_log_id` in the retrieved `list`.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// The `has_more` property is used for pagination to indicate there are additional results.
     pub has_more: bool,
 }
diff --git a/async-openai/src/types/admin/project_api_keys/project_api_keys_.rs b/async-openai/src/types/admin/project_api_keys/project_api_keys_.rs
index 2d339d7b..85e34e29 100644
--- a/async-openai/src/types/admin/project_api_keys/project_api_keys_.rs
+++ b/async-openai/src/types/admin/project_api_keys/project_api_keys_.rs
@@ -46,9 +46,9 @@ pub struct ProjectApiKeyListResponse {
     /// The list of project API keys.
     pub data: Vec<ProjectApiKey>,
     /// The ID of the first project API key in the list.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The ID of the last project API key in the list.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// Indicates if there are more project API keys available.
     pub has_more: bool,
 }
diff --git a/async-openai/src/types/admin/project_rate_limits/project_rate_limits_.rs b/async-openai/src/types/admin/project_rate_limits/project_rate_limits_.rs
index 5f4ac7ed..af5c6b5a 100644
--- a/async-openai/src/types/admin/project_rate_limits/project_rate_limits_.rs
+++ b/async-openai/src/types/admin/project_rate_limits/project_rate_limits_.rs
@@ -37,9 +37,9 @@ pub struct ProjectRateLimitListResponse {
     /// The list of project rate limits.
     pub data: Vec<ProjectRateLimit>,
     /// The ID of the first project rate limit in the list.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The ID of the last project rate limit in the list.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// Indicates if there are more project rate limits available.
     pub has_more: bool,
 }
diff --git a/async-openai/src/types/admin/project_service_accounts/project_service_accounts_.rs b/async-openai/src/types/admin/project_service_accounts/project_service_accounts_.rs
index 1ec1ae6a..87277e36 100644
--- a/async-openai/src/types/admin/project_service_accounts/project_service_accounts_.rs
+++ b/async-openai/src/types/admin/project_service_accounts/project_service_accounts_.rs
@@ -25,9 +25,9 @@ pub struct ProjectServiceAccountListResponse {
     /// The list of project service accounts.
     pub data: Vec<ProjectServiceAccount>,
     /// The ID of the first project service account in the list.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The ID of the last project service account in the list.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// Indicates if there are more project service accounts available.
     pub has_more: bool,
 }
diff --git a/async-openai/src/types/admin/project_users/project_users_.rs b/async-openai/src/types/admin/project_users/project_users_.rs
index 5ab9eefe..dbb636bc 100644
--- a/async-openai/src/types/admin/project_users/project_users_.rs
+++ b/async-openai/src/types/admin/project_users/project_users_.rs
@@ -31,8 +31,8 @@ pub enum ProjectUserRole {
 pub struct ProjectUserListResponse {
     pub object: String,
     pub data: Vec<ProjectUser>,
-    pub first_id: String,
-    pub last_id: String,
+    pub first_id: Option<String>,
+    pub last_id: Option<String>,
     pub has_more: String,
 }
 
diff --git a/async-openai/src/types/admin/projects/projects_.rs b/async-openai/src/types/admin/projects/projects_.rs
index 8e4be725..b191276f 100644
--- a/async-openai/src/types/admin/projects/projects_.rs
+++ b/async-openai/src/types/admin/projects/projects_.rs
@@ -32,8 +32,8 @@ pub struct Project {
 pub struct ProjectListResponse {
     pub object: String,
     pub data: Vec<Project>,
-    pub first_id: String,
-    pub last_id: String,
+    pub first_id: Option<String>,
+    pub last_id: Option<String>,
     pub has_more: String,
 }
 
diff --git a/async-openai/src/types/admin/users/users_.rs b/async-openai/src/types/admin/users/users_.rs
index 7094c414..50b517f4 100644
--- a/async-openai/src/types/admin/users/users_.rs
+++ b/async-openai/src/types/admin/users/users_.rs
@@ -26,8 +26,8 @@ pub struct User {
 pub struct UserListResponse {
     pub object: String,
     pub data: Vec<User>,
-    pub first_id: String,
-    pub last_id: String,
+    pub first_id: Option<String>,
+    pub last_id: Option<String>,
     pub has_more: bool,
 }
 
diff --git a/async-openai/src/types/chat/chat_.rs b/async-openai/src/types/chat/chat_.rs
index 4fc7128c..fdce8a85 100644
--- a/async-openai/src/types/chat/chat_.rs
+++ b/async-openai/src/types/chat/chat_.rs
@@ -1203,9 +1203,9 @@ pub struct ChatCompletionList {
     /// An array of chat completion objects.
     pub data: Vec<CreateChatCompletionResponse>,
     /// The identifier of the first chat completion in the data array.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The identifier of the last chat completion in the data array.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// Indicates whether there are more Chat Completions available.
     pub has_more: bool,
 }
@@ -1250,9 +1250,9 @@ pub struct ChatCompletionMessageList {
     /// An array of chat completion message objects.
     pub data: Vec<ChatCompletionMessageListItem>,
     /// The identifier of the first chat message in the data array.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The identifier of the last chat message in the data array.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// Indicates whether there are more chat messages available.
     pub has_more: bool,
 }
diff --git a/async-openai/src/types/evals/eval.rs b/async-openai/src/types/evals/eval.rs
index 7fec5399..808de54d 100644
--- a/async-openai/src/types/evals/eval.rs
+++ b/async-openai/src/types/evals/eval.rs
@@ -250,9 +250,9 @@ pub struct EvalList {
     /// An array of eval objects.
     pub data: Vec<Eval>,
     /// The identifier of the first eval in the data array.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The identifier of the last eval in the data array.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// Indicates whether there are more evals available.
     pub has_more: bool,
 }
@@ -756,9 +756,9 @@ pub struct EvalRunList {
     /// An array of eval run objects.
     pub data: Vec<EvalRun>,
     /// The identifier of the first eval run in the data array.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The identifier of the last eval run in the data array.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// Indicates whether there are more evals available.
     pub has_more: bool,
 }
@@ -904,9 +904,9 @@ pub struct EvalRunOutputItemList {
     /// An array of eval run output item objects.
     pub data: Vec<EvalRunOutputItem>,
     /// The identifier of the first eval run output item in the data array.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The identifier of the last eval run output item in the data array.
-    pub last_id: String,
+    pub last_id: Option<String>,
     /// Indicates whether there are more eval run output items available.
     pub has_more: bool,
 }
diff --git a/async-openai/src/types/responses/conversation.rs b/async-openai/src/types/responses/conversation.rs
index bd87c435..fb0c69d2 100644
--- a/async-openai/src/types/responses/conversation.rs
+++ b/async-openai/src/types/responses/conversation.rs
@@ -91,9 +91,9 @@ pub struct ConversationItemList {
     /// Whether there are more items available.
     pub has_more: bool,
     /// The ID of the first item in the list.
-    pub first_id: String,
+    pub first_id: Option<String>,
     /// The ID of the last item in the list.
-    pub last_id: String,
+    pub last_id: Option<String>,
 }
 
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq)]
diff --git a/examples/conversations/src/main.rs b/examples/conversations/src/main.rs
index cdbcf3bb..611fd5fb 100644
--- a/examples/conversations/src/main.rs
+++ b/examples/conversations/src/main.rs
@@ -52,8 +52,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .await?;
 
     println!("Added {} items", items_list.data.len());
-    println!("First item ID: {}", items_list.first_id);
-    println!("Last item ID: {}\n", items_list.last_id);
+    println!("First item ID: {:?}", items_list.first_id);
+    println!("Last item ID: {:?}\n", items_list.last_id);
 
     // 3. List all items in the conversation
     println!("3. Listing conversation items...");
@@ -80,13 +80,14 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
     // 4. Retrieve a specific item
     if !all_items.data.is_empty() {
         println!("4. Retrieving a specific item...");
-        let first_item_id = &all_items.first_id;
-        let item = client
-            .conversations()
-            .items(&conversation.id)
-            .retrieve(first_item_id)
-            .await?;
-        println!("Retrieved item: {:?}\n", item);
+        if let Some(first_item_id) = all_items.first_id {
+            let item = client
+                .conversations()
+                .items(&conversation.id)
+                .retrieve(&first_item_id)
+                .await?;
+            println!("Retrieved item: {:?}\n", item);
+        }
     }
 
     // 5. Update conversation metadata