diff --git a/tests/e2e/llm_translation/endpoints_client.py b/tests/e2e/llm_translation/endpoints_client.py
index 54461405a23..f60e5e589ff 100644
--- a/tests/e2e/llm_translation/endpoints_client.py
+++ b/tests/e2e/llm_translation/endpoints_client.py
@@ -19,11 +19,30 @@ from e2e_http import StreamingResponse
 from models import ChatMessage, LiteLLMParamsBody
 
 
+class FunctionParameterProperty(BaseModel):
+    type: str
+    description: str | None = None
+
+
+class FunctionParameters(BaseModel):
+    type: Literal["object"] = "object"
+    properties: dict[str, FunctionParameterProperty]
+    required: list[str] = []
+
+
+class ResponsesFunctionTool(BaseModel):
+    type: Literal["function"] = "function"
+    name: str
+    description: str | None = None
+    parameters: FunctionParameters
+
+
 class ResponsesRequest(BaseModel):
     model: str
     input: str
     instructions: str | None = None
     stream: bool = False
+    tools: list[ResponsesFunctionTool] | None = None
 
 
 class MessagesRequest(BaseModel):
@@ -87,6 +106,9 @@ class ResponsesOutputContent(BaseModel):
 class ResponsesOutputItem(BaseModel):
     type: str | None = None
     content: list[ResponsesOutputContent] = []
+    name: str | None = None
+    arguments: str | None = None
+    call_id: str | None = None
 
 
 class ResponsesResult(BaseModel):
@@ -101,6 +123,16 @@ class ResponsesResult(BaseModel):
             content.text or "" for item in self.output for content in item.content
         )
 
+    @property
+    def function_calls(self) -> tuple[ResponsesOutputItem, ...]:
+        return tuple(
+            item
+            for item in self.output
+            if item.type == "function_call"
+            and item.name is not None
+            and item.arguments is not None
+        )
+
 
 class ResponsesStreamEvent(BaseModel):
     event_id: str | None = None
@@ -204,6 +236,20 @@ class EndpointsClient:
             stream=stream,
         )
 
+    def responses_with_tools(
+        self, key: str, model: str, text: str, tools: list[ResponsesFunctionTool]
+    ) -> StreamingResponse:
+        return self._send(
+            "/v1/responses",
+            key,
+            ResponsesRequest(
+                model=model,
+                input=text,
+                instructions="You are a helpful assistant",
+                tools=tools,
+            ),
+        )
+
     def messages(
         self, key: str, model: str, text: str, *, max_tokens: int = 64
     ) -> StreamingResponse:
diff --git a/tests/e2e/llm_translation/test_responses_e2e.py b/tests/e2e/llm_translation/test_responses_e2e.py
index 91c0759f233..f02721f23b5 100644
--- a/tests/e2e/llm_translation/test_responses_e2e.py
+++ b/tests/e2e/llm_translation/test_responses_e2e.py
@@ -7,13 +7,19 @@ litellm-regression-tests/tests/test_inference_endpoints.py.
 
 from __future__ import annotations
 
+import json
+from typing import cast
+
 import pytest
-from pydantic import ValidationError
+from pydantic import BaseModel, ValidationError
 
 from e2e_config import unique_marker
 from e2e_http import require_successful_call
 from endpoints_client import (
     EndpointsClient,
+    FunctionParameterProperty,
+    FunctionParameters,
+    ResponsesFunctionTool,
     ResponsesOutputTextDeltaEvent,
     ResponsesResult,
     ResponsesStreamEventType,
@@ -24,6 +30,10 @@ from models import LiteLLMParamsBody
 pytestmark = pytest.mark.e2e
 
 
+class WeatherArguments(BaseModel):
+    location: str
+
+
 class TestResponses:
     @pytest.mark.covers("llm.responses.openai.basic.nonstream.works")
     def test_responses_returns_completion(
@@ -69,6 +79,71 @@ class TestResponses:
             == "response.completed"
         ), "responses stream did not terminate with response.completed"
 
+    @pytest.mark.covers("llm.responses.openai.basic.nonstream.cost_logged")
+    def test_responses_logs_cost(
+        self, endpoints_client: EndpointsClient, resources: ResourceManager
+    ) -> None:
+        model = f"e2e-responses-{unique_marker()}"
+        model_id = endpoints_client.create_model(
+            model,
+            LiteLLMParamsBody(model="openai/gpt-4o-mini", api_key="os.environ/OPENAI_API_KEY"),
+        )
+        resources.defer(lambda: endpoints_client.delete_model(model_id))
+        key = resources.key()
+
+        result = endpoints_client.responses(key, model, f"reply with one word {unique_marker()}")
+        require_successful_call(result)
+        parsed = ResponsesResult.model_validate_json(result.body)
+        assert parsed.text.strip(), f"/responses returned no output text: {result.body[:300]}"
+        assert result.call_id and parsed.id, f"missing response identifiers: {result.body[:300]}"
+
+        rows = endpoints_client.proxy.poll_logs_for_request_id(
+            parsed.id,
+            predicate=lambda logged_rows: any((row.spend or 0) > 0 for row in logged_rows),
+        )
+        row = next((logged_row for logged_row in rows if (logged_row.spend or 0) > 0), None)
+        assert row is not None, f"no costed spend row for response id {parsed.id}"
+        assert "gpt-4o-mini" in (row.model or ""), f"unexpected spend row model: {row.model}"
+
+    @pytest.mark.covers("llm.responses.openai.tool_use.nonstream.works")
+    def test_responses_returns_function_call(
+        self, endpoints_client: EndpointsClient, resources: ResourceManager
+    ) -> None:
+        model = f"e2e-responses-{unique_marker()}"
+        model_id = endpoints_client.create_model(
+            model,
+            LiteLLMParamsBody(model="openai/gpt-4o-mini", api_key="os.environ/OPENAI_API_KEY"),
+        )
+        resources.defer(lambda: endpoints_client.delete_model(model_id))
+        key = resources.key()
+
+        result = endpoints_client.responses_with_tools(
+            key,
+            model,
+            "What is the weather in San Francisco? Use the get_weather tool.",
+            [
+                ResponsesFunctionTool(
+                    name="get_weather",
+                    description="Get the weather for a location",
+                    parameters=FunctionParameters(
+                        properties={"location": FunctionParameterProperty(type="string")},
+                        required=["location"],
+                    ),
+                )
+            ],
+        )
+        require_successful_call(result)
+        parsed = ResponsesResult.model_validate_json(result.body)
+        function_call = next(
+            (call for call in parsed.function_calls if call.name == "get_weather"),
+            None,
+        )
+        assert function_call is not None, f"no get_weather function call: {result.body[:500]}"
+        assert function_call.arguments is not None
+        raw_arguments = cast(object, json.loads(function_call.arguments))
+        arguments = WeatherArguments.model_validate(raw_arguments)
+        assert arguments.location, f"function call arguments missing location: {function_call.arguments}"
+
 
 def _parse_stream_event(
     event: str,