JSON is lean for data exchange between machines.
But in the LLM economy, the currency is tokens, not bytes.
To an LLM tokenizer, every bracket and quote is a distinct cost. In our tests, this 'syntax tax' accounts for up to 30% of the payload.
We chose a line-oriented format to minimize overhead and maximize the context window for actual commerce data.
I'd say it's not heavy. JSON syntax is pretty lean compared to XML.