diff --git a/Codec/Binary/Base91.hs b/Codec/Binary/Base91.hs
--- a/Codec/Binary/Base91.hs
+++ b/Codec/Binary/Base91.hs
@@ -5,7 +5,8 @@
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TypeFamilies #-}
 
-module Codec.Binary.Base91 (alphabet, decode, encode) where
+-- | A Generic Base91 Encoder & Decoder
+module Codec.Binary.Base91 (alphabet, decode, encode, Input, Output) where
 
 import Data.Bits ((.&.), (.|.), shiftL, shiftR)
 import Data.Char (ord)
@@ -13,7 +14,10 @@
 import Data.MonoTraversable (Element, MonoFoldable, MonoPointed, ofoldl', opoint)
 import Data.Word (Word8)
 
+-- | An input sequence 'i' containing elements of type 'e'.
 type Input i e = (MonoFoldable i, Element i ~ e)
+
+-- | An output sequence 'o' containing elements of type 'e'.
 type Output o e = (MonoPointed o, Element o ~ e, Monoid o)
 
 {-
diff --git a/base91.cabal b/base91.cabal
--- a/base91.cabal
+++ b/base91.cabal
@@ -1,9 +1,9 @@
 Name:                  base91
-Version:               2.0.0
+Version:               2.1.0
 Author:                Alvaro J. Genial
 Maintainer:            ajg
 Homepage:              https://github.com/ajg/base91
-Synopsis:              A Base91 Encoder & Decoder
+Synopsis:              A Generic Base91 Encoder & Decoder
 Description:           An implementation of Base91 encoding & decoding of arbitrary bytes (octets)
                        to/from characters (all in the ASCII printable range)
 License:               MIT