diff --git a/lib/mutant/actor.rb b/lib/mutant/actor.rb
index 175a09b1..87521a32 100644
--- a/lib/mutant/actor.rb
+++ b/lib/mutant/actor.rb
@@ -32,6 +32,8 @@ module Mutant
       #
       # @return [Message]
       #
+      # @api private
+      #
       def self.new(_type, _payload = Undefined)
         super
       end
@@ -48,6 +50,8 @@ module Mutant
       #
       # @return [Object]
       #
+      # @api private
+      #
       def call(type)
         other.call(Message.new(type, actor.sender))
         message = actor.receiver.call
diff --git a/lib/mutant/actor/actor.rb b/lib/mutant/actor/actor.rb
index 58243310..1f9b67bd 100644
--- a/lib/mutant/actor/actor.rb
+++ b/lib/mutant/actor/actor.rb
@@ -39,6 +39,8 @@ module Mutant
       #
       # @return [Binding]
       #
+      # @api private
+      #
       def bind(other)
         Binding.new(self, other)
       end
diff --git a/lib/mutant/mutator/node.rb b/lib/mutant/mutator/node.rb
index 1bcf0b45..3a9a6a07 100644
--- a/lib/mutant/mutator/node.rb
+++ b/lib/mutant/mutator/node.rb
@@ -219,7 +219,7 @@ module Mutant
       #
       # @return [Enumerable<Fixnum>]
       #
-      # @api pirvate
+      # @api private
       #
       def children_indices(range)
         range_end = range.end
diff --git a/lib/mutant/reporter/cli.rb b/lib/mutant/reporter/cli.rb
index 14820f23..b227a950 100644
--- a/lib/mutant/reporter/cli.rb
+++ b/lib/mutant/reporter/cli.rb
@@ -28,6 +28,8 @@ module Mutant
       #
       # @param [Env] env
       #
+      # @return [self]
+      #
       # @api private
       #
       def start(env)
diff --git a/lib/mutant/reporter/cli/printer.rb b/lib/mutant/reporter/cli/printer.rb
index d11f0db2..e1eecc60 100644
--- a/lib/mutant/reporter/cli/printer.rb
+++ b/lib/mutant/reporter/cli/printer.rb
@@ -159,6 +159,8 @@ module Mutant
           #
           # @return [undefined]
           #
+          # @api private
+          #
           def job_status
             return if active_jobs.empty?
             info('Active Jobs:')
@@ -545,6 +547,14 @@ module Mutant
             puts(object.output)
           end
 
+          # Test if test result is successful
+          #
+          # Only used to determine color.
+          #
+          # @return [false]
+          #
+          # @api private
+          #
           def success?
             false
           end
diff --git a/lib/mutant/runner/master.rb b/lib/mutant/runner/master.rb
index a6a885f9..db8929de 100644
--- a/lib/mutant/runner/master.rb
+++ b/lib/mutant/runner/master.rb
@@ -96,6 +96,10 @@ module Mutant
       #
       # @param [Actor::Sender] sender
       #
+      # @return [undefined]
+      #
+      # @api private
+      #
       def handle_status(sender)
         sender.call(Actor::Message.new(:status, @scheduler.status))
       end
@@ -106,6 +110,8 @@ module Mutant
       #
       # @return [undefined]
       #
+      # @api private
+      #
       def handle_result(job_result)
         return if @stopping
         @scheduler.job_result(job_result)
diff --git a/lib/mutant/runner/worker.rb b/lib/mutant/runner/worker.rb
index e4c57d12..d5bf1dc0 100644
--- a/lib/mutant/runner/worker.rb
+++ b/lib/mutant/runner/worker.rb
@@ -43,6 +43,8 @@ module Mutant
       #
       # @return [Boolean]
       #
+      # @api private
+      #
       def handle(message)
         type, payload = message.type, message.payload
         case message.type