Congrats! This author found a sub-optimal microservice and replaced it with inline code. This is the bread and butter work of good engineering. This is also part of the reason that microservices are dangerous.

The bad engineering part is writing your own replacement for something that already exists. As other commenters here have noted, there were already two separate implementations of JSONata in Go. Why spend $400 to have Claude rewrite something when you can just use an already existing, already supported library?