Why not use INI files?
INI is a very old and quite readable configuration format for small configuration files. It is still used by many programs today and it has some advantages due to this - e.g. python has inbuilt parser for it.
Unfortunately it suffers from two major problems:
- Different parsers will operate in subtly different ways that can lead to often obscure edge case bugs regarding the way whitespace is used, case sensitivity, comments and escape characters.
- It doesn't let you represent hierarchical data.
TOML is a configuration format designed to address these two concerns, although it also suffers from obscure edge case bugs.