diff --git a/src/openai_schemas.py b/src/openai_schemas.py
index 5b54ddd9..9f4a0928 100644
--- a/src/openai_schemas.py
+++ b/src/openai_schemas.py
@@ -72,13 +72,36 @@ class UsageStats:
  cache_creation_tokens: int = 0
 
 
-@dataclass(frozen=True)
+@dataclass(frozen=True, init=False)
 class NormalizedResponse:
  text: str
  tool_calls: tuple[ToolCall, ...]
  usage: UsageStats
  raw_response: Any
 
+ def __init__(
+  self,
+  text: str,
+  tool_calls: tuple[ToolCall, ...] = (),
+  usage: UsageStats | None = None,
+  raw_response: Any = None,
+  usage_input_tokens: int | None = None,
+  usage_output_tokens: int | None = None,
+  usage_cache_read_tokens: int | None = None,
+  usage_cache_creation_tokens: int | None = None,
+ ) -> None:
+  if usage is None:
+   usage = UsageStats(
+    input_tokens=usage_input_tokens if usage_input_tokens is not None else 0,
+    output_tokens=usage_output_tokens if usage_output_tokens is not None else 0,
+    cache_read_tokens=usage_cache_read_tokens if usage_cache_read_tokens is not None else 0,
+    cache_creation_tokens=usage_cache_creation_tokens if usage_cache_creation_tokens is not None else 0,
+   )
+  object.__setattr__(self, "text", text)
+  object.__setattr__(self, "tool_calls", tool_calls)
+  object.__setattr__(self, "usage", usage)
+  object.__setattr__(self, "raw_response", raw_response)
+
  def to_legacy_dict(self) -> JsonValue:
   return {
    "text": self.text,