diff --git a/composer.go b/composer.go
index 91796e5..f15b38a 100644
--- a/composer.go
+++ b/composer.go
@@ -1,5 +1,8 @@
 package tusd
 
+// StoreComposer represents a composable data store. It consists of the core
+// data store and optional extensions. Please consult the package's overview
+// for a more detailed introduction in how to use this structure.
 type StoreComposer struct {
 	Core DataStore
 
@@ -15,11 +18,15 @@ type StoreComposer struct {
 	Concater       ConcaterDataStore
 }
 
+// NewStoreComposer creates a new and empty store composer.
 func NewStoreComposer() *StoreComposer {
 	return &StoreComposer{}
 }
 
-func NewStoreComposerFromDataStore(store DataStore) *StoreComposer {
+// newStoreComposerFromDataStore creates a new store composer and attempts to
+// extract the extensions for the provided store. This is intended to be used
+// for transitioning from data stores to composers.
+func newStoreComposerFromDataStore(store DataStore) *StoreComposer {
 	composer := NewStoreComposer()
 	composer.UseCore(store)
 
@@ -42,6 +49,8 @@ func NewStoreComposerFromDataStore(store DataStore) *StoreComposer {
 	return composer
 }
 
+// Capabilities returns a string representing the provided extensions in a
+// human-readable format meant for debugging.
 func (store *StoreComposer) Capabilities() string {
 	str := "Core: "
 
@@ -85,27 +94,29 @@ func (store *StoreComposer) Capabilities() string {
 	return str
 }
 
+// UseCore will set the used core data store. If the argument is nil, the
+// property will be unset.
 func (store *StoreComposer) UseCore(core DataStore) {
 	store.Core = core
 }
 
-func (store *StoreComposer) UseTerminater(x TerminaterDataStore) {
-	store.UsesTerminater = x != nil
-	store.Terminater = x
+func (store *StoreComposer) UseTerminater(ext TerminaterDataStore) {
+	store.UsesTerminater = ext != nil
+	store.Terminater = ext
 }
-func (store *StoreComposer) UseFinisher(x FinisherDataStore) {
-	store.UsesFinisher = x != nil
-	store.Finisher = x
+func (store *StoreComposer) UseFinisher(ext FinisherDataStore) {
+	store.UsesFinisher = ext != nil
+	store.Finisher = ext
 }
-func (store *StoreComposer) UseLocker(x LockerDataStore) {
-	store.UsesLocker = x != nil
-	store.Locker = x
+func (store *StoreComposer) UseLocker(ext LockerDataStore) {
+	store.UsesLocker = ext != nil
+	store.Locker = ext
 }
-func (store *StoreComposer) UseGetReader(x GetReaderDataStore) {
-	store.UsesGetReader = x != nil
-	store.GetReader = x
+func (store *StoreComposer) UseGetReader(ext GetReaderDataStore) {
+	store.UsesGetReader = ext != nil
+	store.GetReader = ext
 }
-func (store *StoreComposer) UseConcater(x ConcaterDataStore) {
-	store.UsesConcater = x != nil
-	store.Concater = x
+func (store *StoreComposer) UseConcater(ext ConcaterDataStore) {
+	store.UsesConcater = ext != nil
+	store.Concater = ext
 }
diff --git a/composer.mgo b/composer.mgo
index 67733fc..32db7ea 100644
--- a/composer.mgo
+++ b/composer.mgo
@@ -1,8 +1,9 @@
 package tusd
 
-#define USE_FUNC(TYPE) func (store *StoreComposer) Use ## TYPE(x TYPE ## DataStore) { \
-  store.Uses ## TYPE = x != nil; \
-  store.TYPE = x; \
+#define USE_FUNC(TYPE) \
+func (store *StoreComposer) Use ## TYPE(ext TYPE ## DataStore) { \
+  store.Uses ## TYPE = ext != nil; \
+  store.TYPE = ext; \
 }
 
 #define USE_FIELD(TYPE) Uses ## TYPE bool; \
@@ -19,6 +20,9 @@ if store.Uses ## TYPE { \
   str += "✗" \
 }
 
+// StoreComposer represents a composable data store. It consists of the core
+// data store and optional extensions. Please consult the package's overview
+// for a more detailed introduction in how to use this structure.
 type StoreComposer struct {
   Core DataStore
 
@@ -29,11 +33,15 @@ type StoreComposer struct {
   USE_FIELD(Concater)
 }
 
+// NewStoreComposer creates a new and empty store composer.
 func NewStoreComposer() *StoreComposer {
   return &StoreComposer{}
 }
 
-func NewStoreComposerFromDataStore(store DataStore) *StoreComposer {
+// newStoreComposerFromDataStore creates a new store composer and attempts to
+// extract the extensions for the provided store. This is intended to be used
+// for transitioning from data stores to composers.
+func newStoreComposerFromDataStore(store DataStore) *StoreComposer {
   composer := NewStoreComposer()
   composer.UseCore(store)
 
@@ -46,6 +54,8 @@ func NewStoreComposerFromDataStore(store DataStore) *StoreComposer {
   return composer
 }
 
+// Capabilities returns a string representing the provided extensions in a
+// human-readable format meant for debugging.
 func (store *StoreComposer) Capabilities() string {
   str := "Core: "
 
@@ -64,6 +74,8 @@ func (store *StoreComposer) Capabilities() string {
   return str
 }
 
+// UseCore will set the used core data store. If the argument is nil, the
+// property will be unset.
 func (store *StoreComposer) UseCore(core DataStore) {
   store.Core = core
 }
diff --git a/config.go b/config.go
index 055026e..3e5e144 100644
--- a/config.go
+++ b/config.go
@@ -55,7 +55,7 @@ func (config *Config) validate() error {
 	config.isAbs = uri.IsAbs()
 
 	if config.StoreComposer == nil {
-		config.StoreComposer = NewStoreComposerFromDataStore(config.DataStore)
+		config.StoreComposer = newStoreComposerFromDataStore(config.DataStore)
 	} else if config.DataStore != nil {
 		// TODO: consider returning an error
 	}
diff --git a/consullocker/consullocker.go b/consullocker/consullocker.go
index de6a273..8f9cbfc 100644
--- a/consullocker/consullocker.go
+++ b/consullocker/consullocker.go
@@ -45,6 +45,7 @@ func New(client *consul.Client) *ConsulLocker {
 	}
 }
 
+// UseIn adds this locker to the passed composer.
 func (locker *ConsulLocker) UseIn(composer *tusd.StoreComposer) {
 	composer.UseLocker(locker)
 }
diff --git a/filestore/filestore.go b/filestore/filestore.go
index 8dc1cf2..5dfe299 100644
--- a/filestore/filestore.go
+++ b/filestore/filestore.go
@@ -46,6 +46,8 @@ func New(path string) FileStore {
 	return FileStore{path}
 }
 
+// UseIn sets this store as the core data store in the passed composer and adds
+// all possible extension to it.
 func (store FileStore) UseIn(composer *tusd.StoreComposer) {
 	composer.UseCore(store)
 	composer.UseGetReader(store)
diff --git a/memorylocker/memorylocker.go b/memorylocker/memorylocker.go
index e2827f5..a4ea689 100644
--- a/memorylocker/memorylocker.go
+++ b/memorylocker/memorylocker.go
@@ -39,6 +39,7 @@ func New() *MemoryLocker {
 	}
 }
 
+// UseIn adds this locker to the passed composer.
 func (locker *MemoryLocker) UseIn(composer *tusd.StoreComposer) {
 	composer.UseLocker(locker)
 }
diff --git a/s3store/s3store.go b/s3store/s3store.go
index 20f88c7..e4401e7 100644
--- a/s3store/s3store.go
+++ b/s3store/s3store.go
@@ -131,6 +131,8 @@ func New(bucket string, service s3iface.S3API) S3Store {
 	}
 }
 
+// UseIn sets this store as the core data store in the passed composer and adds
+// all possible extension to it.
 func (store S3Store) UseIn(composer *tusd.StoreComposer) {
 	composer.UseCore(store)
 	composer.UseTerminater(store)