diff --git a/.coveralls.yml b/.coveralls.yml
new file mode 100644
index 0000000..9160059
--- /dev/null
+++ b/.coveralls.yml
@@ -0,0 +1 @@
+service_name: travis-ci
diff --git a/.travis.yml b/.travis.yml
index 8a8ac56..7f4a405 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,3 +1,5 @@
 language: ruby
 rvm:
+  - 1.9.3
+  - 2.0.0
   - 2.1.2
diff --git a/README.md b/README.md
index a9e3f47..a8ba3ab 100644
--- a/README.md
+++ b/README.md
@@ -1,19 +1,26 @@
-# YoClient [![Build Status](https://travis-ci.org/youcune/yo_client.svg?branch=master)](https://travis-ci.org/youcune/yo_client)
+# YoClient
 
 is a Ruby client of [Yo](http://www.justyo.co/).
+[![Build Status](https://travis-ci.org/youcune/yo_client.svg?branch=master)](https://travis-ci.org/youcune/yo_client)
+[![Coverage Status](https://coveralls.io/repos/youcune/yo_client/badge.png)](https://coveralls.io/r/youcune/yo_client)
+
+## Requirements
+
+* Ruby 1.9+ (Tested on Ruby 1.9.3, 2.0.0, 2.1.2)
+* [Yo API Account](http://dev.justyo.co/)
 
 ## Installation
 
 Add this line to your application's Gemfile:
 
 ```
-gem 'yo_client', github: 'youcune/yo_client'
+gem 'yo_client'
 ```
 
 And then execute:
 
 ```
-$ bundle
+$ bundle install
 ```
 
 ## Usage
@@ -21,17 +28,24 @@ $ bundle
 ```
 client = YoClient::Client.new(API_TOKEN)
 
-# Send A Yo To All Subscribers
+# Yo all subscribers
 client.yoall
 
-# Yo Individual Usernames
-# Note that USERNAME will be upcased and sent to API
+# Yo specific user
+# Note that USERNAME will be upcased before sending to API
 client.yo(USERNAME)
 
 # Count Total Subscribers
 client.subscribers_count # -> 5
 ```
 
+### Error Handling
+
+* `YoClient::ConnectionError` is risen if the connection has failed.
+* `YoClient::ClientError` is risen if the connection has succeeded but API returned error.
+
+At the date of 13th July, even if API results in failure, it sometimes behaves as if it succeed. In this case, YoClient cannot tell succeeded or not.
+
 ## Contributing
 
 1. Fork it ( https://github.com/youcune/yo_client/fork )
@@ -40,3 +54,12 @@ client.subscribers_count # -> 5
 4. Push to the branch (`git push origin my-new-feature`)
 5. Create a new Pull Request
 
+## Yo the author
+
+[Yo YOUCUNE](http://justyo.co/YOUCUNE), author of YoClient, if you ...
+
+* like YoClient
+* dislike YoClient
+* have any ideas about YoClient
+
+Thanks.
diff --git a/lib/yo_client.rb b/lib/yo_client.rb
index e18138c..e6930d9 100644
--- a/lib/yo_client.rb
+++ b/lib/yo_client.rb
@@ -5,7 +5,7 @@
 module YoClient
   class Client
     # Constructor
-    # @param [String] token Yo API Token
+    # @param [String] api_token Yo API Token
     def initialize(api_token)
       @api_token = api_token
       @faraday = Faraday.new(url: 'http://api.justyo.co') do |faraday|
@@ -16,26 +16,58 @@ def initialize(api_token)
     end
 
     # Yo to all subscribers
+    # @return [Boolean] if request has succeed
     def yoall
-      @faraday.post '/yoall/', token_hash
+      response = connection_wrapper {
+        @faraday.post '/yoall/', token_hash
+      }
+      response.success?
     end
 
     # Yo to specific user
-    # @param [String] username
+    # @param [String] username usename to send yo
+    # @return [Boolean] if request has succeed
     def yo(username)
-      @faraday.post '/yo/', token_hash.merge(username: username.upcase)
+      response = connection_wrapper {
+        @faraday.post '/yo/', token_hash.merge(username: username.upcase)
+      }
+      response.success?
     end
 
     # Get a number of subscribers
     # @return [Integer] number of subscribers
     def subscribers_count
-      response = @faraday.get '/subscribers_count/', token_hash
+      response = connection_wrapper {
+        @faraday.get '/subscribers_count/', token_hash
+      }
       response.body['result']
     end
 
     private
+      # Connect with error handling
+      # @param [Proc] block
+      def connection_wrapper(&block)
+        begin
+          response = block.call
+          raise ClientError.new(response.body['error']) if response.body.has_key?('error')
+        rescue Faraday::ParsingError => e
+          # Has gotten a response, but it is not formatted with JSON
+          raise ClientError.new(e.message)
+        rescue Faraday::ClientError => e
+          # Failed to build a connection
+          raise ConnectionError.new(e.message)
+        end
+
+        response
+      end
+
+      # Returns hash for every request
+      # @return [Hash] hash for every request
       def token_hash
         { api_token: @api_token }
       end
   end
+
+  class ConnectionError < StandardError; end
+  class ClientError < StandardError; end
 end
diff --git a/lib/yo_client/version.rb b/lib/yo_client/version.rb
index 1e5fcbc..3d41400 100644
--- a/lib/yo_client/version.rb
+++ b/lib/yo_client/version.rb
@@ -1,3 +1,3 @@
 module YoClient
-  VERSION = '0.0.2'
+  VERSION = '0.0.3'
 end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 044ba13..e21eb4c 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,3 +1,7 @@
 $LOAD_PATH.unshift File.expand_path('../../lib', __FILE__)
 require 'yo_client'
-require 'pry'
+
+if ENV['TRAVIS']
+  require 'coveralls'
+  Coveralls.wear!
+end
diff --git a/spec/yo_client_spec.rb b/spec/yo_client_spec.rb
index 05daad4..1a147d6 100644
--- a/spec/yo_client_spec.rb
+++ b/spec/yo_client_spec.rb
@@ -18,8 +18,8 @@
       it 'hooks POST /yoall/' do
         expect_any_instance_of(Faraday::Connection).to(
           receive(:post)
-          .with('/yoall/', { api_token: 'test' })
-          .and_return(double('yo', body: {}))
+            .with('/yoall/', { api_token: 'test' })
+            .and_return(double('yo', body: {}, success?: true))
         )
         @client.yoall
       end
@@ -29,8 +29,8 @@
       it 'hooks POST /yo/' do
         expect_any_instance_of(Faraday::Connection).to(
           receive(:post)
-          .with('/yo/', { api_token: 'test', username: 'YOUCUNE' })
-          .and_return(double('yo', body: {}))
+            .with('/yo/', { api_token: 'test', username: 'YOUCUNE' })
+            .and_return(double('yo', body: {}, success?: true))
         )
         @client.yo('youcune')
       end
@@ -40,7 +40,6 @@
       it 'hooks GET /subscribers_count/' do
         expect_any_instance_of(Faraday::Connection).to(
           receive(:get)
-            .with('/subscribers_count/', { api_token: 'test' })
             .and_return(double('subscribers_count', body: { 'result' => 5 }))
         )
         expect(@client.subscribers_count).to eq 5
diff --git a/yo_client.gemspec b/yo_client.gemspec
index eddb630..cc884a4 100644
--- a/yo_client.gemspec
+++ b/yo_client.gemspec
@@ -8,8 +8,8 @@ Gem::Specification.new do |spec|
   spec.version       = YoClient::VERSION
   spec.authors       = ['Yu Nakanishi']
   spec.email         = ['you@nakanishi.email']
-  spec.summary       = 'Yo Client Library'
-  spec.description   = 'Yo Client Library'
+  spec.summary       = 'Yo (http://www.justyo.co/) Ruby Client'
+  spec.description   = 'Yo (http://www.justyo.co/) Ruby Client'
   spec.homepage      = 'https://github.com/youcune/yo_client'
   spec.license       = 'MIT'
 
@@ -20,8 +20,9 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency 'bundler', '~> 1.6'
   spec.add_development_dependency 'rake'
-  spec.add_development_dependency 'rspec'
-  spec.add_development_dependency 'pry-byebug'
-  spec.add_dependency 'faraday'
-  spec.add_dependency 'faraday_middleware'
+  spec.add_development_dependency 'rspec', '~> 3.0.0'
+  spec.add_development_dependency 'coveralls'
+  spec.add_dependency 'faraday', '~> 0.9.0'
+  spec.add_dependency 'faraday_middleware', '~> 0.9.0'
+  spec.required_ruby_version = '>= 1.9'
 end