I'm quite fond of DataWeave for this, as an FP-inspired data transformation language with plenty of built-ins, including support for XML, JSON and beyond [0].

Apparently there's an online playground [1] and Beta support for LSP now [2]. I've only ever used it in a containerized-Java setting.

[0]: https://mjdresdner.medium.com/dataweave-2-x-playground-comin...

[1]: http://dwlang.fun/

[2]: https://github.com/mulesoft-labs/data-weave-language-server