Parsing your data format completely via tree-sitter is an interesting choice. Usually tree-sitter is "the second parser" only (for syntax highlighting etc), and the t-s version of a grammar isn't 100% comprehensive.
https://github.com/42futures/firm/blob/31fc084b7c7855bef9694...
I do wonder how much value all this work adds compared to having e.g. JSONC files with schemas. (Or HCL-syntax-for-JSON to visually match this work and then JSON schemas.)