TOML quickly breaks down with lots of nested arrays of objects. For example: a: b: - c: 1 - d: - e: 2 - f: g:

TOML quickly breaks down with lots of nested arrays of objects. For example: a: b: - c: 1 - d: - e: 2 - f: g: 3 Turns into this, which is unreadable: [[a.b]] c = 1 [[a.b]] [[a.b.d]] e = 2 [[a.b.d]] [a.b.d.f] g = 3 TOML also has a few restrictions, such as not supporting mixed-type arrays like [1, "hello", true], or arrays at the root of the data. JSON can represent any TOML value (as far as I know), but TOML cannot represent any JSON value. At my company we use YAML a lot for table-driven tests (e.g. [1]), and this not only means lots of nested arrays, but also having to represent pure data (i.e. the expected output of a test), which requires a format that supports encoding arbitrary "pure" data structures of arrays, numbers, strings, booleans, and objects. [1] https://github.com/sanity-io/groq-test-suite/ https://github.com/sanity-io/groq-test-suite/