Visualizing Tone in Chat with IBM Watson and a Blink(1)

Metamind's sentiment analysis tool[1] is probably about the best you can get, especially for short text. Try the "Tweet" version (a tab on that page or available separately[2]).

Sentiment on short text is pretty hard. Metamind claims 81.73%[3], although that appears to be for general text (not just Tweets). Anything above ~70% accuracy would be competitive with the state of the art on Twitter data[4].

[1] https://www.metamind.io/classifiers/155

[2] https://www.metamind.io/language/twitter

[3] https://www.metamind.io/classifiers/155/stats

[4] http://www.lrec-conf.org/proceedings/lrec2014/pdf/483_Paper....