Python: Convert nested SDK models in hosted tool sanitization

python/packages/foundry/agent_framework_foundry/_tools.py

@@ -33,6 +33,17 @@ def _validate_hosted_tool_payload(sanitized: Mapping[str, Any]) -> None:
         )
 
 
+def _to_plain_dict(value: Any) -> Any:
+    """Recursively convert Azure SDK models and mappings into plain dictionaries."""
+    if hasattr(value, "as_dict") and callable(value.as_dict):
+        return _to_plain_dict(value.as_dict())
+    if isinstance(value, Mapping):
+        return {k: _to_plain_dict(v) for k, v in value.items()}
+    if isinstance(value, (list, tuple)):
+        return [_to_plain_dict(v) for v in value]
+    return value
+
+
 def _sanitize_foundry_response_tool(tool_item: Any) -> Any:  # pyright: ignore[reportUnusedFunction]
     """Return a Responses-API-safe tool payload for Foundry hosted tools.
 
@@ -50,9 +61,12 @@ def _sanitize_foundry_response_tool(tool_item: Any) -> Any:  # pyright: ignore[r
        defaulted (``file_search`` without ``vector_store_ids``, ``mcp`` without
        either ``server_url`` or ``project_connection_id``) raise ``ValueError``
        with a message that points at the tool definition.
+    4. Nested Azure SDK models (such as ``BingCustomSearchToolParameters`` or
+       ``AutoCodeInterpreterToolParam``) are recursively converted into plain
+       dictionaries so the resulting payload is JSON serializable.
     """
     if isinstance(tool_item, FoundryMCPTool):
-        sanitized: dict[str, Any] = dict(cast("Mapping[str, Any]", tool_item))
+        sanitized: dict[str, Any] = _to_plain_dict(tool_item)
         sanitized.pop("name", None)
         sanitized.pop("description", None)
         _validate_hosted_tool_payload(sanitized)
@@ -61,7 +75,7 @@ def _sanitize_foundry_response_tool(tool_item: Any) -> Any:  # pyright: ignore[r
     if isinstance(tool_item, Mapping):
         mapping = cast("Mapping[str, Any]", tool_item)
         if "type" in mapping and mapping.get("type") not in {"function", "custom"}:
-            sanitized = dict(mapping)
+            sanitized = _to_plain_dict(mapping)
             sanitized.pop("name", None)
             sanitized.pop("description", None)
             if sanitized.get("type") == "code_interpreter" and "container" not in sanitized:

python/packages/foundry/tests/foundry/test_foundry_chat_client.py

@@ -1320,6 +1320,43 @@ def test_prepare_tools_for_openai_strips_name_from_non_function_hosted_tool_dict
     assert "description" not in response_tools[1]
 
 
+def test_prepare_tools_for_openai_serializes_bing_custom_search_tool() -> None:
+    """Hosted Bing custom search tool contains nested models that must be JSON serializable."""
+    project_client = MagicMock()
+    project_client.get_openai_client.return_value = _make_mock_openai_client()
+    client = FoundryChatClient(project_client=project_client, model="test-model")
+
+    tool = FoundryChatClient.get_bing_custom_search_tool(
+        connection_id="/subscriptions/x/connections/bing",
+        instance_name="inst",
+        market="zh-TW",
+    )
+
+    response_tools = client._prepare_tools_for_openai([tool])
+
+    assert len(response_tools) == 1
+    # Ensure nested Azure SDK models were converted and are JSON serializable
+    dumped = json.dumps(response_tools)
+    assert "bing_custom_search_preview" in dumped
+    assert "project_connection_id" in dumped
+    assert "inst" in dumped
+
+
+def test_prepare_tools_for_openai_serializes_code_interpreter_with_auto_param() -> None:
+    """Hosted code interpreter tool from factory must be JSON serializable."""
+    project_client = MagicMock()
+    project_client.get_openai_client.return_value = _make_mock_openai_client()
+    client = FoundryChatClient(project_client=project_client, model="test-model")
+
+    tool = FoundryChatClient.get_code_interpreter_tool()
+    response_tools = client._prepare_tools_for_openai([tool])
+
+    assert len(response_tools) == 1
+    dumped = json.dumps(response_tools)
+    assert "code_interpreter" in dumped
+    assert "auto" in dumped
+
+
 @pytest.mark.flaky
 @pytest.mark.integration
 @skip_if_foundry_integration_tests_disabled