fix: Preserved nullable object fields by carrying schema properties

litellm/llms/vertex_ai/common_utils.py

@@ -1,4 +1,5 @@
 import re
+from copy import deepcopy
 from enum import Enum
 from typing import Any, Dict, List, Literal, Optional, Set, Tuple, Union, get_type_hints
 
@@ -617,7 +618,7 @@ def convert_anyof_null_to_nullable(schema, depth=0):
     if anyof is not None:
         contains_null = False
         for atype in anyof:
-            if atype == {"type": "null"}:
+            if isinstance(atype, dict) and atype.get("type") == "null":
                 # remove null type
                 anyof.remove(atype)
                 contains_null = True
@@ -735,7 +736,20 @@ def _convert_schema_types(schema, depth=0):
         type_val = schema["type"]
         if isinstance(type_val, list) and len(type_val) > 1:
             # Convert ["string", "number"] -> {"anyOf": [{"type": "STRING"}, {"type": "NUMBER"}]}
-            schema["anyOf"] = [{"type": t} for t in type_val if isinstance(t, str)]
+            # Preserve other schema fields by copying them into each non-null anyOf item.
+            base_schema = {k: v for k, v in schema.items() if k not in {"type", "anyOf"}}
+            any_of: List[Dict[str, Any]] = []
+            for t in type_val:
+                if not isinstance(t, str):
+                    continue
+                if t == "null":
+                    # Keep null entry minimal so we can strip it later.
+                    any_of.append({"type": "null"})
+                    continue
+                item_schema = deepcopy(base_schema)
+                item_schema["type"] = t
+                any_of.append(item_schema)
+            schema["anyOf"] = any_of
             schema.pop("type")
         elif isinstance(type_val, list) and len(type_val) == 1:
             schema["type"] = type_val[0]

tests/local_testing/test_amazing_vertex_completion.py

@@ -3598,6 +3598,60 @@ def test_vertex_schema_test():
     print(response)
 
 
+def test_gemini_nullable_object_tool_schema_httpx():
+    """
+    Ensure nullable object tool params preserve nested properties in Vertex schema conversion.
+    """
+    load_vertex_ai_credentials()
+    litellm._turn_on_debug()
+
+
+    tools = [{
+            "type": "function",
+            "strict": True,
+            "function": {
+                "name": "create_support_ticket",
+                "description": "Create a paid user support ticket",
+                "parameters": {
+                    "type": "object",
+                    "additionalProperties": False,
+                    "required": ["ticket_id", "customer_context"],
+                    "properties": {
+                        "ticket_id": {
+                            "type": "string",
+                            "description": "Unique identifier for the support ticket"
+                        },
+                        "customer_context": {
+                            "type": ["object", "null"],
+                            "description": "Context about the paid customer, if available",
+                            "additionalProperties": False,
+                            "required": ["user_id", "plan"],
+                            "properties": {
+                                "user_id": {
+                                    "type": "string",
+                                    "description": "Internal user identifier"
+                                },
+                                "plan": {
+                                    "type": "string",
+                                    "description": "Subscription plan name (e.g. pro, enterprise)"
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }]
+
+    response = litellm.completion(
+        model="vertex_ai/gemini-2.5-flash",
+        messages=[{"role": "user", "content": "call the tool"}],
+        tools=tools,
+        tool_choice="required",
+    )
+
+    print(response)
+
+
 def test_vertex_ai_response_id():
     """Test that litellm preserves the response ID from Vertex AI's API for non-streaming responses"""
     from litellm.llms.custom_httpx.http_handler import HTTPHandler