A: Hey Stefan, thanks for asking!

REST API and webhooks are both on the roadmap, still being scoped. Webhooks is probably the more useful of the two for most integration setups (Zapier, n8n, custom workflows all run off them). Worth dropping upvotes on both to push them up the list:
https://honeybill.featurebase.app/p/webhooks-for-invoice-events
https://honeybill.featurebase.app/p/public-api

MCP isn't on our roadmap yet (welcome to add though) - If it becomes the right shape for HoneyBill we could certainly build.

Cheers!