diff --git a/ollama/_utils.py b/ollama/_utils.py
index 15f1cc0c..9bc2ba14 100644
--- a/ollama/_utils.py
+++ b/ollama/_utils.py
@@ -60,7 +60,11 @@ def convert_function_to_tool(func: Callable) -> Tool:
     func.__name__,
     (pydantic.BaseModel,),
     {
-      '__annotations__': {k: v.annotation if v.annotation != inspect._empty else str for k, v in inspect.signature(func).parameters.items()},
+      '__annotations__': {
+        k: v.annotation if v.annotation != inspect._empty else str
+        for k, v in inspect.signature(func).parameters.items()
+        if v.kind not in (inspect.Parameter.VAR_POSITIONAL, inspect.Parameter.VAR_KEYWORD)
+      },
       '__signature__': inspect.signature(func),
       '__doc__': parsed_docstring[doc_string_hash],
     },