diff --git a/qcelemental/models/align.py b/qcelemental/models/align.py
index 00db470a..aa3a8358 100644
--- a/qcelemental/models/align.py
+++ b/qcelemental/models/align.py
@@ -1,5 +1,7 @@
+from typing import Optional
+
 import numpy as np
-from pydantic import validator
+from pydantic import Field, validator
 
 from ..util import blockwise_contract, blockwise_expand
 from .basemodels import ProtoModel
@@ -19,10 +21,18 @@ class AlignmentMill(ProtoModel):
 
     """
 
-    shift: Array[float]  # type: ignore
-    rotation: Array[float]  # type: ignore
-    atommap: Array[int]  # type: ignore
-    mirror: bool = False
+    shift: Optional[Array[float]] = Field(  # type: ignore
+        None, description="Translation array (3,) for coordinates.",
+    )
+    rotation: Optional[Array[float]] = Field(  # type: ignore
+        None, description="Rotation array (3, 3) for coordinates.",
+    )
+    atommap: Optional[Array[int]] = Field(  # type: ignore
+        None, description="Atom exchange map (nat,) for coordinates.",
+    )
+    mirror: bool = Field(
+        False, description="Do mirror invert coordinates?",
+    )
 
     class Config:
         force_skip_defaults = True
diff --git a/qcelemental/models/types.py b/qcelemental/models/types.py
index 8457efbb..ee961535 100644
--- a/qcelemental/models/types.py
+++ b/qcelemental/models/types.py
@@ -1,3 +1,5 @@
+from typing import Any, Dict
+
 import numpy as np
 
 
@@ -15,6 +17,19 @@ def validate(cls, v):
 
         return v
 
+    @classmethod
+    def __modify_schema__(cls, field_schema: Dict[str, Any]) -> None:
+        dt = cls._dtype
+        if dt is int or np.issubdtype(dt, np.integer):
+            items = {"type": "number", "multipleOf": 1.0}
+        elif dt is float or np.issubdtype(dt, np.floating):
+            items = {"type": "number"}
+        elif dt is str or np.issubdtype(dt, np.string_):
+            items = {"type": "string"}
+        elif dt is bool or np.issubdtype(dt, np.bool_):
+            items = {"type": "boolean"}
+        field_schema.update(type="array", items=items)
+
 
 class ArrayMeta(type):
     def __getitem__(self, dtype):