diff --git a/monoidal-containers.cabal b/monoidal-containers.cabal
--- a/monoidal-containers.cabal
+++ b/monoidal-containers.cabal
@@ -1,7 +1,19 @@
 name:                monoidal-containers
-version:             0.3.0.0
+version:             0.3.0.1
 synopsis:            Containers with monoidal accumulation
-description:         Containers with monoidal accumulation
+description:
+    Containers with merging via monoidal accumulation. The 'Monoid' instances
+    provided by the @containers@ and @unordered-containers@ packages merge
+    structures in a left-biased manner instead of using the underlying monoidal
+    structure of the value.
+    .
+    This package wraps the types provided by these packages, but provides @Monoid@
+    instances implemented in terms of the value type's 'mappend'. For instance,
+    the @Monoid@ @Map@ instance looks like,
+    .
+    @
+    instance (Ord k, Monoid a) => Monoid (MonoidalMap k a)
+    @
 homepage:            http://github.com/bgamari/monoidal-containers
 license:             BSD3
 license-file:        LICENSE
diff --git a/src/Data/HashMap/Monoidal.hs b/src/Data/HashMap/Monoidal.hs
--- a/src/Data/HashMap/Monoidal.hs
+++ b/src/Data/HashMap/Monoidal.hs
@@ -16,7 +16,7 @@
 -- underlying 'Map'.
 
 module Data.HashMap.Monoidal
-    ( MonoidalHashMap
+    ( MonoidalHashMap(..)
       -- * Often-needed functions
     , toList
     , fromList
diff --git a/src/Data/Map/Monoidal.hs b/src/Data/Map/Monoidal.hs
--- a/src/Data/Map/Monoidal.hs
+++ b/src/Data/Map/Monoidal.hs
@@ -16,7 +16,7 @@
 -- underlying 'Map'.
 
 module Data.Map.Monoidal
-    ( MonoidalMap
+    ( MonoidalMap(..)
       -- * Often-needed functions
     , singleton
     , size
diff --git a/src/Data/Map/Monoidal/Strict.hs b/src/Data/Map/Monoidal/Strict.hs
--- a/src/Data/Map/Monoidal/Strict.hs
+++ b/src/Data/Map/Monoidal/Strict.hs
@@ -16,7 +16,7 @@
 -- underlying 'Map'.
 
 module Data.Map.Monoidal.Strict
-    ( MonoidalMap
+    ( MonoidalMap(..)
       -- * Often-needed functions
     , singleton
     , size