bitcoin-wallet-api/spec — pull request #1 by oleganza (2014-06-22 17:43:29+00:00)
Title: Removed INSUFFICIENT_FUNDS constant for security reasons. 

We may consider different status codes for some integration errors. E.g. when wallet is not active/available so the user could try to fix the problem. This status code would allow someone to figure out how much money user's wallet has.