From b07555d26f4c7ad9a2d1ec45428a9d4287db612c Mon Sep 17 00:00:00 2001
From: Andrew Xia <axia@meta.com>
Date: Tue, 25 Nov 2025 10:27:26 -0800
Subject: [PATCH] [responsesAPI][2] parse ResponseFunctionToolCallOutputItem
 (#29383)

Signed-off-by: Andrew Xia <axia@fb.com>
Co-authored-by: Andrew Xia <axia@fb.com>
---
 tests/entrypoints/test_responses_utils.py | 15 +++++++++++++++
 vllm/entrypoints/openai/protocol.py       |  5 +----
 vllm/entrypoints/responses_utils.py       |  9 +++++++++
 3 files changed, 25 insertions(+), 4 deletions(-)

diff --git a/tests/entrypoints/test_responses_utils.py b/tests/entrypoints/test_responses_utils.py
index 91c818374e3fd..893d806b65742 100644
--- a/tests/entrypoints/test_responses_utils.py
+++ b/tests/entrypoints/test_responses_utils.py
@@ -2,6 +2,9 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 import pytest
+from openai.types.responses.response_function_tool_call_output_item import (
+    ResponseFunctionToolCallOutputItem,
+)
 from openai.types.responses.response_reasoning_item import (
     Content,
     ResponseReasoningItem,
@@ -76,6 +79,18 @@ class TestResponsesUtils:
             == 'Hmm, the user has just started with a simple "Hello,"'
         )
 
+        tool_call_output = ResponseFunctionToolCallOutputItem(
+            id="temp_id",
+            type="function_call_output",
+            call_id="temp",
+            output="1234",
+            status="completed",
+        )
+        formatted_item = construct_chat_message_with_tool_call(tool_call_output)
+        assert formatted_item["role"] == "tool"
+        assert formatted_item["content"] == "1234"
+        assert formatted_item["tool_call_id"] == "temp"
+
         item = ResponseReasoningItem(
             id="lol",
             summary=[],
diff --git a/vllm/entrypoints/openai/protocol.py b/vllm/entrypoints/openai/protocol.py
index 98a385a1dcd5f..688ea9697d9d6 100644
--- a/vllm/entrypoints/openai/protocol.py
+++ b/vllm/entrypoints/openai/protocol.py
@@ -29,7 +29,6 @@ from openai.types.responses import (
     ResponseOutputItemAddedEvent,
     ResponseOutputItemDoneEvent,
     ResponsePrompt,
-    ResponseReasoningItem,
     ResponseReasoningTextDeltaEvent,
     ResponseReasoningTextDoneEvent,
     ResponseStatus,
@@ -304,9 +303,7 @@ def get_logits_processors(
     return None
 
 
-ResponseInputOutputItem: TypeAlias = (
-    ResponseInputItemParam | ResponseReasoningItem | ResponseFunctionToolCall
-)
+ResponseInputOutputItem: TypeAlias = ResponseInputItemParam | ResponseOutputItem
 
 
 class ResponsesRequest(OpenAIBaseModel):
diff --git a/vllm/entrypoints/responses_utils.py b/vllm/entrypoints/responses_utils.py
index b02c43c7f8246..07abb80ebc9e3 100644
--- a/vllm/entrypoints/responses_utils.py
+++ b/vllm/entrypoints/responses_utils.py
@@ -10,6 +10,9 @@ from openai.types.chat.chat_completion_message_tool_call_param import (
     Function as FunctionCallTool,
 )
 from openai.types.responses import ResponseFunctionToolCall, ResponseOutputItem
+from openai.types.responses.response_function_tool_call_output_item import (
+    ResponseFunctionToolCallOutputItem,
+)
 from openai.types.responses.response_output_message import ResponseOutputMessage
 from openai.types.responses.response_reasoning_item import ResponseReasoningItem
 from openai.types.responses.tool import Tool
@@ -94,6 +97,12 @@ def construct_chat_message_with_tool_call(
             "role": "assistant",
             "reasoning": reasoning_content,
         }
+    elif isinstance(item, ResponseFunctionToolCallOutputItem):
+        return ChatCompletionToolMessageParam(
+            role="tool",
+            content=item.output,
+            tool_call_id=item.call_id,
+        )
     elif item.get("type") == "function_call_output":
         # Append the function call output as a tool message.
         return ChatCompletionToolMessageParam(