diff --git a/vllm_middleware.py b/vllm_middleware.py
index 39270c4..fa94f12 100644
--- a/vllm_middleware.py
+++ b/vllm_middleware.py
@@ -145,13 +145,26 @@ async def proxy(path: str, request: Request):
                     stripped_any = True
 
             # Fix tool function parameters: must be object, not array/null/missing
+            # Also fix nested: parameters.properties must be object, not array
             tools = data.get("tools")
             if isinstance(tools, list):
                 for tool in tools:
                     func = tool.get("function") if isinstance(tool, dict) else None
-                    if isinstance(func, dict) and not isinstance(func.get("parameters"), dict):
+                    if not isinstance(func, dict):
+                        continue
+                    params = func.get("parameters")
+                    if not isinstance(params, dict):
                         func["parameters"] = {"type": "object", "properties": {}}
                         stripped_any = True
+                    else:
+                        # Fix nested: properties must be object, not array
+                        if not isinstance(params.get("properties"), dict):
+                            params["properties"] = {}
+                            stripped_any = True
+                        # required must be a list of strings if present
+                        if "required" in params and not isinstance(params["required"], list):
+                            del params["required"]
+                            stripped_any = True
 
             if stripped_any:
                 body = json.dumps(data).encode()