That`s is valid for search engines. But if JSON-LD was sufficient for agents, Google wouldn't have launched UCP (Universal Commerce Protocol) yesterday.
Took a look, UCP looks like presenting an entire shopping lifecycle for agents.
JSON-LD is just read-only metadata for machines.
True. But extracting that metadata requires parsing the full DOM. CommerceTXT is for efficient discovery. Scan inventory cheaply first, then commit to the transaction.