diff --git a/src/motile_toolbox/candidate_graph/__init__.py b/src/motile_toolbox/candidate_graph/__init__.py
index efd4cbb..d06fd4e 100644
--- a/src/motile_toolbox/candidate_graph/__init__.py
+++ b/src/motile_toolbox/candidate_graph/__init__.py
@@ -1,2 +1,3 @@
+from .graph_attributes import EdgeAttr, NodeAttr
 from .graph_from_segmentation import graph_from_segmentation
 from .graph_to_nx import graph_to_nx
diff --git a/src/motile_toolbox/candidate_graph/graph_attributes.py b/src/motile_toolbox/candidate_graph/graph_attributes.py
new file mode 100644
index 0000000..767e023
--- /dev/null
+++ b/src/motile_toolbox/candidate_graph/graph_attributes.py
@@ -0,0 +1,19 @@
+from enum import Enum
+
+
+class NodeAttr(Enum):
+    """Node attributes that can be added to candidate graph using the toolbox.
+    Note: Motile can flexibly support any custom attributes. The toolbox provides
+    implementations of commonly used ones, listed here.
+    """
+
+    SEG_ID = "segmentation_id"
+
+
+class EdgeAttr(Enum):
+    """Edge attributes that can be added to candidate graph using the toolbox.
+    Note: Motile can flexibly support any custom attributes. The toolbox provides
+    implementations of commonly used ones, listed here.
+    """
+
+    DISTANCE = "distance"
diff --git a/src/motile_toolbox/candidate_graph/graph_from_segmentation.py b/src/motile_toolbox/candidate_graph/graph_from_segmentation.py
index 96c0879..42fe480 100644
--- a/src/motile_toolbox/candidate_graph/graph_from_segmentation.py
+++ b/src/motile_toolbox/candidate_graph/graph_from_segmentation.py
@@ -7,6 +7,8 @@
 from skimage.measure import regionprops
 from tqdm import tqdm
 
+from .graph_attributes import EdgeAttr, NodeAttr
+
 logger = logging.getLogger(__name__)
 
 
@@ -33,7 +35,7 @@ def _get_location(
 
 def nodes_from_segmentation(
     segmentation: np.ndarray,
-    attributes: tuple[str, ...] | list[str] = ("segmentation_id",),
+    attributes: tuple[NodeAttr, ...] | list[NodeAttr] = (NodeAttr.SEG_ID,),
     position_keys: tuple[str, ...] | list[str] = ("y", "x"),
     frame_key: str = "t",
 ) -> tuple[nx.DiGraph, dict[int, list[Any]]]:
@@ -73,8 +75,8 @@ def nodes_from_segmentation(
             attrs = {
                 frame_key: t,
             }
-            if "segmentation_id" in attributes:
-                attrs["segmentation_id"] = regionprop.label
+            if NodeAttr.SEG_ID in attributes:
+                attrs[NodeAttr.SEG_ID.value] = regionprop.label
             centroid = regionprop.centroid  # [z,] y, x
             for label, value in zip(position_keys, centroid):
                 attrs[label] = value
@@ -88,7 +90,7 @@ def nodes_from_segmentation(
 def add_cand_edges(
     cand_graph: nx.DiGraph,
     max_edge_distance: float,
-    attributes: tuple[str, ...] | list[str] = ("distance",),
+    attributes: tuple[EdgeAttr, ...] | list[EdgeAttr] = (EdgeAttr.DISTANCE,),
     position_keys: tuple[str, ...] | list[str] = ("y", "x"),
     frame_key: str = "t",
     node_frame_dict: None | dict[int, list[Any]] = None,
@@ -133,8 +135,8 @@ def add_cand_edges(
             for next_id, next_loc in zip(next_nodes, next_locs):
                 dist = math.dist(next_loc, loc)
                 attrs = {}
-                if "distance" in attributes:
-                    attrs["distance"] = dist
+                if EdgeAttr.DISTANCE in attributes:
+                    attrs[EdgeAttr.DISTANCE.value] = dist
                 if dist <= max_edge_distance:
                     cand_graph.add_edge(node, next_id, **attrs)
 
@@ -142,8 +144,8 @@ def add_cand_edges(
 def graph_from_segmentation(
     segmentation: np.ndarray,
     max_edge_distance: float,
-    node_attributes: tuple[str, ...] | list[str] = ("segmentation_id",),
-    edge_attributes: tuple[str, ...] | list[str] = ("distance",),
+    node_attributes: tuple[NodeAttr, ...] | list[NodeAttr] = (NodeAttr.SEG_ID,),
+    edge_attributes: tuple[EdgeAttr, ...] | list[EdgeAttr] = (EdgeAttr.DISTANCE,),
     position_keys: tuple[str, ...] | list[str] = ("y", "x"),
     frame_key: str = "t",
 ):
@@ -181,22 +183,6 @@ def graph_from_segmentation(
             arguments, or if the number of position keys provided does not match the
             number of position dimensions.
     """
-    valid_edge_attributes = [
-        "distance",
-    ]
-    for attr in edge_attributes:
-        if attr not in valid_edge_attributes:
-            raise ValueError(
-                f"Invalid attribute {attr} (supported attrs: {valid_edge_attributes})"
-            )
-    valid_node_attributes = [
-        "segmentation_id",
-    ]
-    for attr in node_attributes:
-        if attr not in valid_node_attributes:
-            raise ValueError(
-                f"Invalid attribute {attr} (supported attrs: {valid_node_attributes})"
-            )
     if len(position_keys) != segmentation.ndim - 1:
         raise ValueError(
             f"Position labels {position_keys} does not match number of spatial dims "
diff --git a/tests/utils/test_loading_utils.py b/tests/test_utils/test_loading_utils.py
similarity index 100%
rename from tests/utils/test_loading_utils.py
rename to tests/test_utils/test_loading_utils.py