diff --git a/mollie-api-haskell.cabal b/mollie-api-haskell.cabal
--- a/mollie-api-haskell.cabal
+++ b/mollie-api-haskell.cabal
@@ -1,5 +1,5 @@
 name:                mollie-api-haskell
-version:             0.1.0.0
+version:             0.1.0.1
 synopsis:            Mollie API client for Haskell http://www.mollie.com
 description:         Please see README.md
 homepage:            https://github.com/paramanders/mollie-api-haskell
diff --git a/src/Mollie/API.hs b/src/Mollie/API.hs
--- a/src/Mollie/API.hs
+++ b/src/Mollie/API.hs
@@ -19,7 +19,8 @@
 
   This key should start with either `test_` or `live_`.
 -}
-createEnv :: Text.Text -> IO Env
+createEnv :: Text.Text -- ^ key
+          -> IO Env
 createEnv key = HTTP.withOpenSSL $ do
     sslContext <- OpenSSL.context
     OpenSSL.contextSetVerificationMode sslContext OpenSSL.VerifyPeer
diff --git a/src/Mollie/API/Customers.hs b/src/Mollie/API/Customers.hs
--- a/src/Mollie/API/Customers.hs
+++ b/src/Mollie/API/Customers.hs
@@ -39,7 +39,9 @@
 {-|
   Helper to create a minimal new customer.
 -}
-newCustomer :: Text.Text -> Text.Text -> NewCustomer
+newCustomer :: Text.Text -- ^ name
+            -> Text.Text -- ^ email
+            -> NewCustomer
 newCustomer name email = NewCustomer
     { newCustomer_name     = name
     , newCustomer_email    = email
@@ -64,7 +66,8 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/customers/get.
 -}
-getCustomer :: Text.Text -> Mollie (Either ResponseError Customer)
+getCustomer :: Text.Text -- ^ customerId
+            -> Mollie (Either ResponseError Customer)
 getCustomer customerId = get path
     where
         path = Text.intercalate "/" [customersPath, customerId]
@@ -74,7 +77,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/customers/list.
 -}
-getCustomers :: Int -> Int -> Mollie (Either ResponseError (List Customer))
+getCustomers :: Int -- ^ offset
+             -> Int -- ^ count
+             -> Mollie (Either ResponseError (List Customer))
 getCustomers offset count = get path
     where
         path = customersPath <> query
@@ -85,7 +90,8 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/customers/create-payment.
 -}
-createCustomerPayment :: Text.Text -> NewPayment -> Mollie (Either ResponseError Payment)
+createCustomerPayment :: Text.Text -- ^ customerId
+                      -> NewPayment -> Mollie (Either ResponseError Payment)
 createCustomerPayment customerId newPayment = do
     result <- send HTTP.methodPost path newPayment
     return $ decodeResult result
@@ -97,7 +103,10 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/customers/list-payments.
 -}
-getCustomerPayments :: Text.Text -> Int -> Int -> Mollie (Either ResponseError (List Payment))
+getCustomerPayments :: Text.Text -- ^ customerId
+                    -> Int -- ^ offset
+                    -> Int -- ^ count
+                    -> Mollie (Either ResponseError (List Payment))
 getCustomerPayments customerId offset count = get path
     where
         path = (Text.intercalate "/" [customersPath, customerId, paymentsPath]) <> query
diff --git a/src/Mollie/API/Issuers.hs b/src/Mollie/API/Issuers.hs
--- a/src/Mollie/API/Issuers.hs
+++ b/src/Mollie/API/Issuers.hs
@@ -28,7 +28,8 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/issuers/get.
 -}
-getIssuer :: Text.Text -> Mollie (Either ResponseError Issuer)
+getIssuer :: Text.Text -- ^ issuerId
+          -> Mollie (Either ResponseError Issuer)
 getIssuer issuerId = get path
     where
         path = (Text.intercalate "/" [issuersPath, issuerId])
@@ -38,7 +39,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/issuers/list.
 -}
-getIssuers :: Int -> Int -> Mollie (Either ResponseError (List Issuer))
+getIssuers :: Int -- ^ offset
+           -> Int -- ^ count
+           -> Mollie (Either ResponseError (List Issuer))
 getIssuers offset count = get path
     where
         path = issuersPath <> query
diff --git a/src/Mollie/API/Mandates.hs b/src/Mollie/API/Mandates.hs
--- a/src/Mollie/API/Mandates.hs
+++ b/src/Mollie/API/Mandates.hs
@@ -33,7 +33,10 @@
 mandatesPath :: Text.Text
 mandatesPath = "mandates"
 
-newMandate :: PaymentMethod -> Text.Text -> Text.Text -> NewMandate
+newMandate :: PaymentMethod
+           -> Text.Text -- ^ consumerName
+           -> Text.Text -- ^ consumerAccount
+           -> NewMandate
 newMandate method consumerName consumerAccount = NewMandate
     { newMandate_method           = method
     , newMandate_consumerName     = consumerName
@@ -48,7 +51,8 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/mandates/create.
 -}
-createCustomerMandate :: Text.Text -> NewMandate -> Mollie (Either ResponseError Mandate)
+createCustomerMandate :: Text.Text -- ^ customerId
+                      -> NewMandate -> Mollie (Either ResponseError Mandate)
 createCustomerMandate customerId newMandate = do
     result <- send HTTP.methodPost path newMandate
     return $ decodeResult result
@@ -60,7 +64,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/mandates/get.
 -}
-getCustomerMandate :: Text.Text -> Text.Text -> Mollie (Either ResponseError Mandate)
+getCustomerMandate :: Text.Text -- ^ customerId
+                   -> Text.Text -- ^ mandateId
+                   -> Mollie (Either ResponseError Mandate)
 getCustomerMandate customerId mandateId = get path
     where
         path = Text.intercalate "/" [customersPath, customerId, mandatesPath, mandateId]
@@ -70,7 +76,10 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/mandates/list.
 -}
-getCustomerMandates :: Text.Text -> Int -> Int -> Mollie (Either ResponseError (List Mandate))
+getCustomerMandates :: Text.Text -- ^ customerId
+                    -> Int -- ^ offset
+                    -> Int -- ^ count
+                    -> Mollie (Either ResponseError (List Mandate))
 getCustomerMandates customerId offset count = get path
     where
         path = (Text.intercalate "/" [customersPath, customerId, mandatesPath]) <> query
diff --git a/src/Mollie/API/Methods.hs b/src/Mollie/API/Methods.hs
--- a/src/Mollie/API/Methods.hs
+++ b/src/Mollie/API/Methods.hs
@@ -32,7 +32,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/methods/get.
 -}
-getMethod :: PaymentMethod -> Text.Text -> Mollie (Either ResponseError Method)
+getMethod :: PaymentMethod
+          -> Text.Text -- ^ locale
+          -> Mollie (Either ResponseError Method)
 getMethod methodId locale = get path
     where
         path = (Text.intercalate "/" [methodsPath, toText methodId]) <> query
@@ -43,7 +45,10 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/methods/list.
 -}
-getMethods :: Text.Text -> Int -> Int -> Mollie (Either ResponseError (List Method))
+getMethods :: Text.Text -- ^ locale
+           -> Int -- ^ offset
+           -> Int -- ^ count
+           -> Mollie (Either ResponseError (List Method))
 getMethods locale offset count = get path
     where
         path = methodsPath <> query
diff --git a/src/Mollie/API/Payments.hs b/src/Mollie/API/Payments.hs
--- a/src/Mollie/API/Payments.hs
+++ b/src/Mollie/API/Payments.hs
@@ -45,7 +45,10 @@
 {-|
   Helper to create a minimal new payment for normal use.
 -}
-newPayment :: Double -> Text.Text -> Text.Text -> NewPayment
+newPayment :: Double -- ^ amount
+           -> Text.Text -- ^ description
+           -> Text.Text -- ^ redirectUrl
+           -> NewPayment
 newPayment amount description redirectUrl = (newRecurringPayment amount description)
     { newPayment_redirectUrl       = Just redirectUrl
     , newPayment_recurringType     = Nothing
@@ -61,7 +64,9 @@
   For a first recurring payment use `newPayment` and set the
   recurring type to `First`, because it needs a return url.
 -}
-newRecurringPayment :: Double -> Text.Text -> NewPayment
+newRecurringPayment :: Double -- ^ amount
+                    -> Text.Text -- ^ description
+                    -> NewPayment
 newRecurringPayment amount description = NewPayment
     { newPayment_amount            = amount
     , newPayment_description       = description
@@ -107,7 +112,8 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/payments/get.
 -}
-getPayment :: Text.Text -> Mollie (Either ResponseError Payment)
+getPayment :: Text.Text -- ^ paymentId
+           -> Mollie (Either ResponseError Payment)
 getPayment paymentId = get path
     where
         path = Text.intercalate "/" [paymentsPath, paymentId]
@@ -117,7 +123,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/payments/list.
 -}
-getPayments :: Int -> Int -> Mollie (Either ResponseError (List Payment))
+getPayments :: Int -- ^ offset
+            -> Int -- ^ count
+            -> Mollie (Either ResponseError (List Payment))
 getPayments offset count = get path
     where
         path = paymentsPath <> query
@@ -137,7 +145,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/refunds/create.
 -}
-createPaymentRefund :: Text.Text -> NewRefund -> Mollie (Either ResponseError Refund)
+createPaymentRefund :: Text.Text -- ^ paymentId
+                    -> NewRefund
+                    -> Mollie (Either ResponseError Refund)
 createPaymentRefund paymentId newRefund = do
     result <- send HTTP.methodPost path newRefund
     return $ decodeResult result
@@ -149,7 +159,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/refunds/get.
 -}
-getPaymentRefund :: Text.Text -> Text.Text -> Mollie (Either ResponseError Refund)
+getPaymentRefund :: Text.Text -- ^ paymentId
+                 -> Text.Text -- ^ refundId
+                 -> Mollie (Either ResponseError Refund)
 getPaymentRefund paymentId refundId = get path
     where
         path = Text.intercalate "/" [paymentsPath, paymentId, refundsPath, refundId]
@@ -161,7 +173,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/refunds/delete.
 -}
-cancelPaymentRefund :: Text.Text -> Text.Text -> Mollie (Maybe ResponseError)
+cancelPaymentRefund :: Text.Text -- ^ paymentId
+                    -> Text.Text -- ^ refundId
+                    -> Mollie (Maybe ResponseError)
 cancelPaymentRefund paymentId refundId = do
     result <- delete path
     return $ ignoreResult result
@@ -173,7 +187,10 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/refunds/list.
 -}
-getPaymentRefunds :: Text.Text -> Int -> Int -> Mollie (Either ResponseError (List Refund))
+getPaymentRefunds :: Text.Text -- ^ paymentId
+                  -> Int -- ^ offset
+                  -> Int -- ^ count
+                  -> Mollie (Either ResponseError (List Refund))
 getPaymentRefunds paymentId offset count = get path
     where
         path = (Text.intercalate "/" [paymentsPath, paymentId, refundsPath]) <> query
diff --git a/src/Mollie/API/Refunds.hs b/src/Mollie/API/Refunds.hs
--- a/src/Mollie/API/Refunds.hs
+++ b/src/Mollie/API/Refunds.hs
@@ -27,7 +27,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/refunds/list-all.
 -}
-getRefunds :: Int -> Int -> Mollie (Either ResponseError (List Refund))
+getRefunds :: Int -- ^ offset
+           -> Int -- ^ count
+           -> Mollie (Either ResponseError (List Refund))
 getRefunds offset count = get path
     where
         path = refundsPath <> query
diff --git a/src/Mollie/API/Subscriptions.hs b/src/Mollie/API/Subscriptions.hs
--- a/src/Mollie/API/Subscriptions.hs
+++ b/src/Mollie/API/Subscriptions.hs
@@ -33,8 +33,14 @@
 
 {-|
   Helper to create a minimal new subscription. Defaults to an ongoing subscription.
+
+  The interval is in human readable format and support the following values:
+  `1 day`/`n days`, `1 week`/`n weeks`, `1 month`/`n months` where n > 1.
 -}
-newSubscription :: Double -> Text.Text -> Text.Text -> NewSubscription
+newSubscription :: Double -- ^ amount
+                -> Text.Text -- ^ interval
+                -> Text.Text -- ^ description
+                -> NewSubscription
 newSubscription amount interval description = NewSubscription
     { newSubscription_amount      = amount
     , newSubscription_times       = Nothing
@@ -49,7 +55,8 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/subscriptions/create.
 -}
-createCustomerSubscription :: Text.Text -> NewSubscription -> Mollie (Either ResponseError Subscription)
+createCustomerSubscription :: Text.Text -- ^ customerId
+                           -> NewSubscription -> Mollie (Either ResponseError Subscription)
 createCustomerSubscription customerId newSubscription = do
     result <- send HTTP.methodPost path newSubscription
     return $ decodeResult result
@@ -61,7 +68,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/subscriptions/get.
 -}
-getCustomerSubscription :: Text.Text -> Text.Text -> Mollie (Either ResponseError Subscription)
+getCustomerSubscription :: Text.Text -- ^ customerId
+                        -> Text.Text -- ^ subscriptionId
+                        -> Mollie (Either ResponseError Subscription)
 getCustomerSubscription customerId subscriptionId = get path
     where
         path = Text.intercalate "/" [customersPath, customerId, subscriptionsPath, subscriptionId]
@@ -71,7 +80,10 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/subscriptions/list.
 -}
-getCustomerSubscriptions :: Text.Text -> Int -> Int -> Mollie (Either ResponseError (List Subscription))
+getCustomerSubscriptions :: Text.Text -- ^ customerId
+                         -> Int -- ^ offset
+                         -> Int -- ^ count
+                         -> Mollie (Either ResponseError (List Subscription))
 getCustomerSubscriptions customerId offset count = get path
     where
         path = (Text.intercalate "/" [customersPath, customerId, subscriptionsPath]) <> query
@@ -82,7 +94,9 @@
 
   For more information see: https://www.mollie.com/en/docs/reference/subscriptions/delete.
 -}
-cancelCustomerSubscription :: Text.Text -> Text.Text -> Mollie (Either ResponseError Subscription)
+cancelCustomerSubscription :: Text.Text -- ^ customerId
+                           -> Text.Text -- ^ subscriptionId
+                           -> Mollie (Either ResponseError Subscription)
 cancelCustomerSubscription customerId subscriptionId = do
     result <- delete path
     return $ decodeResult result