diff --git a/src/PaymentServer/Processors/Stripe.hs b/src/PaymentServer/Processors/Stripe.hs
index ec03171ac2b1e03494df692cfc2aafedcb3b53b2..36cc53519cdda3ad4b1b08717efedad7a1f66811 100644
--- a/src/PaymentServer/Processors/Stripe.hs
+++ b/src/PaymentServer/Processors/Stripe.hs
@@ -131,10 +131,12 @@ webhook d _ =
 type ChargesAPI = "charge" :> ReqBody '[JSON] Charges :> Post '[JSON] Acknowledgement
 
 data Charges = Charges
-  { token :: Text
-  , voucher :: Voucher
-  , amount :: Int
-  , currency :: Text
+  { token :: Text          -- ^ The text of a Stripe tokenized payment method.
+  , voucher :: Voucher     -- ^ The voucher for which this charge will pay.
+  , amount :: Int          -- ^ The amount of the charge in the minimum
+                           -- currency unit of the target currency (eg for
+                           -- USD, cents).
+  , currency :: Text       -- ^ The currency in which the charge will be made.
   } deriving (Show, Eq)
 
 instance FromJSON Charges where