diff --git a/instructor/function_calls.py b/instructor/function_calls.py
index 9b34e13e6..b8e70ea37 100644
--- a/instructor/function_calls.py
+++ b/instructor/function_calls.py
@@ -294,6 +294,10 @@ def parse_anthropic_tools(
         validation_context: Optional[dict[str, Any]] = None,
         strict: Optional[bool] = None,
     ) -> BaseModel:
+        from anthropic.types import Message
+        if isinstance(completion, Message) and completion.stop_reason == 'max_tokens':
+            raise IncompleteOutputException(last_completion=completion)
+
         # Anthropic returns arguments as a dict, dump to json for model validation below
         tool_calls = [
             json.dumps(c.input) for c in completion.content if c.type == "tool_use"
@@ -319,6 +323,9 @@ def parse_anthropic_json(
 
         assert isinstance(completion, Message)
 
+        if completion.stop_reason == 'max_tokens':
+            raise IncompleteOutputException(last_completion=completion)
+
         text = completion.content[0].text
         extra_text = extract_json_from_codeblock(text)