diff --git a/lib/rackstash/encoder.rb b/lib/rackstash/encoder.rb
index 7c8a52a..dc472be 100644
--- a/lib/rackstash/encoder.rb
+++ b/lib/rackstash/encoder.rb
@@ -26,6 +26,10 @@ module Rackstash
   # deal with events on their own.
   module Encoder
     class << self
+      # Register an encoder with one or more given names. These names can then
+      # be used in {.build} to fetch the registered class and build a new
+      # encoder object for it.
+      #
       # @param encoder_class [Class] a class from which a new encoder can be
       #   created. Filter objects must respond to `encode` and accept an event
       #   hash.
diff --git a/lib/rackstash/filter.rb b/lib/rackstash/filter.rb
index f871e16..da3ad56 100644
--- a/lib/rackstash/filter.rb
+++ b/lib/rackstash/filter.rb
@@ -24,6 +24,10 @@ module Rackstash
   # class inside this module.
   module Filter
     class << self
+      # Register a filter with one or more given names. These names can then be
+      # used in {.build} to fetch the registered class and build a new filter
+      # object for it.
+      #
       # @param filter_class [Class] a class from which a new filter can be
       #   created. Filter objects must respond to `call` and accept an event
       #   hash.