Getting Started The MTH API makes it possible for you to submit, edit, and retrieve the data contained within your account. In order to use the API, you will need your unique API Key located on the REST API page. You can have multiple keys, so you can create many applications which will use their own keys. It will be much more secure than to use one key in all the applications. Do not give out these keys to anyone! The key works like your password, and protects your data.