diff --git a/sgl-model-gateway/src/routers/openai/responses/mcp.rs b/sgl-model-gateway/src/routers/openai/responses/mcp.rs
index 8f2ae7a62..75425ba90 100644
--- a/sgl-model-gateway/src/routers/openai/responses/mcp.rs
+++ b/sgl-model-gateway/src/routers/openai/responses/mcp.rs
@@ -198,8 +198,8 @@ pub(super) async fn execute_streaming_tool_calls(
 // Payload Transformation
 // ============================================================================
 
-/// Transform payload to replace MCP tools with function tools for streaming
-pub(super) fn prepare_mcp_payload_for_streaming(
+/// Transform payload to replace MCP tools with function tools
+pub(super) fn prepare_mcp_tools_as_functions(
     payload: &mut Value,
     active_mcp: &Arc<mcp::McpManager>,
     server_keys: &[String],
diff --git a/sgl-model-gateway/src/routers/openai/responses/non_streaming.rs b/sgl-model-gateway/src/routers/openai/responses/non_streaming.rs
index f02d9f3e2..51c7ae3fd 100644
--- a/sgl-model-gateway/src/routers/openai/responses/non_streaming.rs
+++ b/sgl-model-gateway/src/routers/openai/responses/non_streaming.rs
@@ -11,8 +11,8 @@ use serde_json::{json, Value};
 use tracing::warn;
 
 use super::{
-    mcp::{execute_tool_loop, prepare_mcp_payload_for_streaming},
-    utils::{mask_tools_as_mcp, patch_streaming_response_json},
+    mcp::{execute_tool_loop, prepare_mcp_tools_as_functions},
+    utils::{mask_tools_as_mcp, patch_response_with_request_metadata},
 };
 use crate::routers::{
     header_utils::{apply_provider_headers, extract_auth_header},
@@ -71,7 +71,7 @@ pub async fn handle_non_streaming_response(mut ctx: RequestContext) -> Response
             server_keys: server_keys.clone(),
             ..McpLoopConfig::default()
         };
-        prepare_mcp_payload_for_streaming(&mut payload, mcp, &server_keys);
+        prepare_mcp_tools_as_functions(&mut payload, mcp, &server_keys);
 
         match execute_tool_loop(
             ctx.components.client(),
@@ -140,7 +140,7 @@ pub async fn handle_non_streaming_response(mut ctx: RequestContext) -> Response
     }
 
     mask_tools_as_mcp(&mut response_json, original_body);
-    patch_streaming_response_json(
+    patch_response_with_request_metadata(
         &mut response_json,
         original_body,
         previous_response_id.as_deref(),
diff --git a/sgl-model-gateway/src/routers/openai/responses/streaming.rs b/sgl-model-gateway/src/routers/openai/responses/streaming.rs
index 2176d5cf4..2c820517b 100644
--- a/sgl-model-gateway/src/routers/openai/responses/streaming.rs
+++ b/sgl-model-gateway/src/routers/openai/responses/streaming.rs
@@ -26,10 +26,10 @@ use super::{
     common::{extract_output_index, get_event_type, parse_sse_block, ChunkProcessor},
     mcp::{
         build_resume_payload, execute_streaming_tool_calls, inject_mcp_metadata_streaming,
-        prepare_mcp_payload_for_streaming, send_mcp_list_tools_events, ToolLoopState,
+        prepare_mcp_tools_as_functions, send_mcp_list_tools_events, ToolLoopState,
     },
     tool_handler::{StreamAction, StreamingToolHandler},
-    utils::{mask_tools_as_mcp, patch_streaming_response_json, rewrite_streaming_block},
+    utils::{mask_tools_as_mcp, patch_response_with_request_metadata, rewrite_streaming_block},
 };
 use crate::{
     protocols::{
@@ -452,7 +452,7 @@ pub(super) fn send_final_response_event(
     }
 
     mask_tools_as_mcp(&mut final_response, ctx.original_request);
-    patch_streaming_response_json(
+    patch_response_with_request_metadata(
         &mut final_response,
         ctx.original_request,
         ctx.previous_response_id,
@@ -590,7 +590,7 @@ pub(super) async fn handle_simple_streaming_passthrough(
             }
             let encountered_error = accumulator.encountered_error().cloned();
             if let Some(mut response_json) = accumulator.into_final_response() {
-                patch_streaming_response_json(
+                patch_response_with_request_metadata(
                     &mut response_json,
                     &original_request,
                     previous_response_id.as_deref(),
@@ -642,7 +642,7 @@ pub(super) async fn handle_streaming_with_tool_interception(
 ) -> Response {
     // Transform MCP tools to function tools in payload
     let mut payload = req.payload;
-    prepare_mcp_payload_for_streaming(&mut payload, active_mcp, &server_keys);
+    prepare_mcp_tools_as_functions(&mut payload, active_mcp, &server_keys);
 
     let (tx, rx) = mpsc::unbounded_channel::<Result<Bytes, io::Error>>();
     let should_store = req.original_body.store.unwrap_or(false);
@@ -885,7 +885,7 @@ pub(super) async fn handle_streaming_with_tool_interception(
                     );
 
                     mask_tools_as_mcp(&mut response_json, &original_request);
-                    patch_streaming_response_json(
+                    patch_response_with_request_metadata(
                         &mut response_json,
                         &original_request,
                         previous_response_id.as_deref(),
diff --git a/sgl-model-gateway/src/routers/openai/responses/utils.rs b/sgl-model-gateway/src/routers/openai/responses/utils.rs
index f3b51ef5b..d85bdfad2 100644
--- a/sgl-model-gateway/src/routers/openai/responses/utils.rs
+++ b/sgl-model-gateway/src/routers/openai/responses/utils.rs
@@ -26,8 +26,17 @@ where
     }
 }
 
-/// Patch streaming response JSON with metadata from original request
-pub(super) fn patch_streaming_response_json(
+/// Patch response JSON with metadata from original request
+///
+/// The upstream response may be missing fields that were in the original request.
+/// This function ensures these fields are preserved in the final response:
+/// - `previous_response_id` - conversation threading
+/// - `instructions` - system instructions
+/// - `metadata` - user-provided metadata
+/// - `store` - whether to persist the response
+/// - `model` - model identifier
+/// - `safety_identifier` - user identifier for safety
+pub(super) fn patch_response_with_request_metadata(
     response_json: &mut Value,
     original_body: &ResponsesRequest,
     original_previous_response_id: Option<&str>,