I've always thought of TOML as not far off a superset of the configparser format, although with a different API in code. I realise most tools don't use the extent of configparser, but coming from JSON and YAML, I always found the more advanced configparser features counter-intuitive and awkward to use. I'm not a huge fan of TOML, but it has the necessary primitive values (strings, numbers, booleans), and some reasonable structures for managing collections and nesting.