diff --git a/src/nnbench/types.py b/src/nnbench/types.py
index f497378..52d51df 100644
--- a/src/nnbench/types.py
+++ b/src/nnbench/types.py
@@ -7,6 +7,7 @@
 from typing import Any, Callable, Generic, TypedDict, TypeVar
 
 T = TypeVar("T")
+Variable = tuple[str, type]
 
 
 class BenchmarkResult(TypedDict):
@@ -104,9 +105,9 @@ def __post_init__(self):
 
 @dataclass(frozen=True)
 class Interface:
-    varnames: tuple[str, ...]
-    vartypes: tuple[type, ...]
-    varitems: tuple[tuple[str, inspect.Parameter], ...]
+    names: tuple[str, ...]
+    types: tuple[type, ...]
+    variables: tuple[Variable, ...]
     defaults: dict[str, Any]
 
     @classmethod
@@ -115,6 +116,6 @@ def from_callable(cls, fn: Callable) -> Interface:
         return cls(
             tuple(sig.parameters.keys()),
             tuple(p.annotation for p in sig.parameters.values()),
-            tuple(sig.parameters.items()),
+            tuple((k, v.annotation) for k, v in sig.parameters.items()),
             {n: p.default for n, p in sig.parameters.items()},
         )
diff --git a/tests/test_benchmark_cls.py b/tests/test_benchmark_cls.py
index b697c7f..07c48a6 100644
--- a/tests/test_benchmark_cls.py
+++ b/tests/test_benchmark_cls.py
@@ -8,9 +8,9 @@ def empty_function() -> None:
         pass
 
     interface = types.Interface.from_callable(empty_function)
-    assert interface.varnames == ()
-    assert interface.vartypes == ()
-    assert interface.varitems == ()
+    assert interface.names == ()
+    assert interface.types == ()
+    assert interface.variables == ()
     assert interface.defaults == {}
 
 
@@ -19,14 +19,13 @@ def complex_function(a: int, b, c: str = "hello", d: float = 10.0) -> None:  # t
         pass
 
     interface = types.Interface.from_callable(complex_function)
-    assert interface.varnames == ("a", "b", "c", "d")
-    assert interface.vartypes == (
+    assert interface.names == ("a", "b", "c", "d")
+    assert interface.types == (
         int,
         inspect._empty,
         str,
         float,
     )
 
-    varitems = [(param.name, param.annotation) for name, param in interface.varitems]
-    assert varitems == [("a", int), ("b", inspect._empty), ("c", str), ("d", float)]
+    assert interface.variables == (("a", int), ("b", inspect._empty), ("c", str), ("d", float))
     assert interface.defaults == {"a": inspect._empty, "b": inspect._empty, "c": "hello", "d": 10.0}