diff --git a/homeassistant/components/open_router/entity.py b/homeassistant/components/open_router/entity.py
index 6667514a93a..ea3aa9d1d82 100644
--- a/homeassistant/components/open_router/entity.py
+++ b/homeassistant/components/open_router/entity.py
@@ -88,9 +88,13 @@ def _format_tool(
     custom_serializer: Callable[[Any], Any] | None,
 ) -> ChatCompletionFunctionToolParam:
     """Format tool specification."""
+    unsupported_keys = {"oneOf", "anyOf", "allOf"}
+    schema = convert(tool.parameters, custom_serializer=custom_serializer)
+    schema = {k: v for k, v in schema.items() if k not in unsupported_keys}
+
     tool_spec = FunctionDefinition(
         name=tool.name,
-        parameters=convert(tool.parameters, custom_serializer=custom_serializer),
+        parameters=schema,
     )
     if tool.description:
         tool_spec["description"] = tool.description