[Bugfix][Responses] Handle additional_tools input items

tests/entrypoints/openai/responses/test_function_call_parsing.py

@@ -6,10 +6,99 @@
 
 import pytest
 from openai.types.responses import ResponseFunctionToolCall, ResponseOutputMessage
+from openai.types.responses.response_item import AdditionalTools
 
 from vllm.entrypoints.openai.responses.protocol import ResponsesRequest
 
 
+def make_function_tool(name: str) -> dict:
+    return {
+        "type": "function",
+        "name": name,
+        "description": f"Call {name}.",
+        "parameters": {
+            "type": "object",
+            "properties": {},
+        },
+    }
+
+
+def test_additional_tools_are_promoted_out_of_input():
+    """Additional tools configure the request and are not chat messages."""
+    request = ResponsesRequest(
+        model="gpt-oss",
+        input=[
+            {
+                "id": "at_123",
+                "type": "additional_tools",
+                "role": "developer",
+                "tools": [make_function_tool("exec")],
+            },
+            {
+                "type": "message",
+                "role": "user",
+                "content": [{"type": "input_text", "text": "Run pwd"}],
+            },
+        ],
+        tool_choice="required",
+    )
+
+    assert len(request.input) == 1
+    assert request.input[0]["type"] == "message"
+    assert [tool.name for tool in request.tools] == ["exec"]
+    assert request.tool_choice == "required"
+
+
+def test_additional_tools_extend_top_level_tools_in_input_order():
+    request = ResponsesRequest(
+        model="gpt-oss",
+        tools=[make_function_tool("top_level")],
+        input=[
+            {
+                "id": "at_123",
+                "type": "additional_tools",
+                "role": "developer",
+                "tools": [make_function_tool("first_additional")],
+            },
+            {
+                "id": "at_456",
+                "type": "additional_tools",
+                "role": "developer",
+                "tools": [make_function_tool("second_additional")],
+            },
+            {
+                "type": "message",
+                "role": "user",
+                "content": [{"type": "input_text", "text": "Hello"}],
+            },
+        ],
+    )
+
+    assert len(request.input) == 1
+    assert [tool.name for tool in request.tools] == [
+        "top_level",
+        "first_additional",
+        "second_additional",
+    ]
+
+
+def test_typed_additional_tools_are_promoted():
+    additional_tools = AdditionalTools(
+        id="at_123",
+        type="additional_tools",
+        role="developer",
+        tools=[make_function_tool("exec")],
+    )
+
+    request = ResponsesRequest(
+        model="gpt-oss",
+        input=[additional_tools, {"role": "user", "content": "Run pwd"}],
+    )
+
+    assert len(request.input) == 1
+    assert [tool.name for tool in request.tools] == ["exec"]
+
+
 def test_function_call_dict_converted_to_object():
     """Test that function_call dictionaries are correctly parsed into
     ResponseFunctionToolCall objects."""

vllm/entrypoints/openai/responses/protocol.py

@@ -42,6 +42,7 @@
     ResponseInProgressEvent as OpenAIResponseInProgressEvent,
 )
 from openai.types.responses.response import IncompleteDetails, ToolChoice
+from openai.types.responses.response_item import AdditionalTools
 from openai.types.responses.response_reasoning_item import (
     Content as ResponseReasoningTextContent,
 )
@@ -605,6 +606,25 @@ def check_tool_usage(cls, data):
         if not isinstance(data, dict):
             return data
 
+        input_data = data.get("input")
+        if isinstance(input_data, list):
+            input_items = []
+            additional_tools = []
+            for item in input_data:
+                if isinstance(item, AdditionalTools):
+                    additional_tools.extend(item.tools)
+                elif isinstance(item, dict) and item.get("type") == "additional_tools":
+                    try:
+                        additional_tools.extend(AdditionalTools(**item).tools)
+                    except ValidationError:
+                        input_items.append(item)
+                else:
+                    input_items.append(item)
+
+            if len(input_items) != len(input_data):
+                data["input"] = input_items
+                data["tools"] = [*(data.get("tools") or []), *additional_tools]
+
         tools = data.get("tools")
         tool_choice = data.get("tool_choice", "auto")
         has_tools = tools is not None and len(tools) > 0