Hi!
No need to worry about spamming this post with suggestions 🙂
First, the main idea of this API is to return plain-text data. While it's tru JSON is an industry standard, I personally like clean results. Basically, with the way the API is made, I just send a request and save the output to a variable and that's it. No need to parse JSON or XML.
Second, definitely. Currently the API doesn't return "errors", but it can be easily enabled.