fix：无参工具在某些api报错

src/llm_models/model_client/openai_client.py

@@ -314,13 +314,15 @@ def _convert_tool_options(tool_options: List[ToolOption]) -> List[ChatCompletion
     """
     converted_tools: List[ChatCompletionToolParam] = []
     for tool_option in tool_options:
+        parameters_schema = cast(
+            Dict[str, object],
+            tool_option.parameters_schema or {"type": "object", "properties": {}},
+        )
         function_schema: FunctionDefinition = {
             "name": tool_option.name,
             "description": tool_option.description,
+            "parameters": parameters_schema,
         }
-        parameters_schema = tool_option.parameters_schema
-        if parameters_schema is not None:
-            function_schema["parameters"] = cast(Dict[str, object], parameters_schema)
         converted_tools.append(
             {
                 "type": "function",

src/llm_models/payload_content/tool_option.py

@@ -88,6 +88,15 @@ def _build_parameters_schema_from_property_map(property_map: Dict[str, Any]) ->
     return parameters_schema
 
 
+def _build_empty_object_schema() -> Dict[str, Any]:
+    """构建无参工具使用的空对象 Schema。"""
+
+    return {
+        "type": "object",
+        "properties": {},
+    }
+
+
 @dataclass(slots=True)
 class ToolParam:
     """工具参数定义。"""
@@ -333,9 +342,8 @@ class ToolOption:
         function_schema: Dict[str, Any] = {
             "name": self.name,
             "description": self.description,
+            "parameters": self.parameters_schema or _build_empty_object_schema(),
         }
-        if self.parameters_schema is not None:
-            function_schema["parameters"] = self.parameters_schema
         return {
             "type": "function",
             "function": function_schema,