diff --git a/curvesim/constants.py b/curvesim/constants.py
index f645eb766..a7471ab95 100644
--- a/curvesim/constants.py
+++ b/curvesim/constants.py
@@ -1,7 +1,33 @@
+"""
+Constants and Enum types used in Curvesim.
+"""
 from enum import Enum
 
 
-class Chain(str, Enum):
+class StrEnum(str, Enum):
+    """
+    Custom string enum type since the builtin `StrEnum` is not available
+    until Python 3.11.
+    """
+
+    def __str__(self):
+        """
+        Regular Enum's __str__ is the name, rather than the value,
+        e.g.
+
+        >>> str(Chain.MAINNET)
+        'Chain.MAINNET'
+
+        so we need to explicit use the value.
+
+        This behaves like the builtin `StrEnum` (available in 3.11).
+        """
+        return str.__str__(self)
+
+
+class Chain(StrEnum):
+    """Identifiers for chains & layer 2s."""
+
     MAINNET = "mainnet"
     ARBITRUM = "arbitrum"
     OPTIMISM = "optimism"
@@ -11,6 +37,8 @@ class Chain(str, Enum):
     XDAI = "xdai"
 
 
-class Env(str, Enum):
+class Env(StrEnum):
+    """Names for different API environments."""
+
     PROD = "prod"
     STAGING = "staging"