ValueTuples lose their property names when serialized

The names are a compiler trick. If you look at the definition for ValueTuple you'll see that its field names are just Item1, Item2, etc.

Since JsonConvert.SerializeObject was compiled well before you assigned names that you could use during your compilation, it cannot recover the names.

Method parameters/return types are decorated with attributes that indicate the names to be used when a method's signature includes ValueTuples. This allows code authored later to "see" the names by the compiler playing tricks again, but that's the "wrong way around" to be of much use here.

How to get the expected output

Introduce an explicit type, if the names of the fields/properties are so important.

How to get the expected output

Something like this:

var myTypes = new{ type = "A", text = "I am an animal"};
var cnvValue = JsonConvert.SerializeObject(myTypes);

should work if you’re looking for a similarly terse approach. Doesn’t use ValueTuples (but anonymous types) under the hood though; this is my interpreting your question as “how can I produce this expected JSON without going to the full extent of declaring a class etc”