Disclosure: I build Schemity, a desktop ERD tool - this post is from our blog and uses it for the examples.
TL;DR: You want AI help with schema design, but NDA and IT policy forbid pasting schemas into cloud AI tools. Schemity's BYOK AI chat sends requests directly from your desktop to your chosen provider with your own key - no vendor server in the middle.
AI is genuinely good at schema design. Describe a booking system in two sentences and a model will sketch the entities, the foreign keys, the junction tables - a solid first draft in seconds. Every engineer who has tried it knows the pull.
And every engineer doing client work knows the catch. Your schema is the most honest document your business owns. Table names alone reveal the product roadmap: subscriptions, usage_credits, partner_payouts. Pasting your CREATE TABLE statements into a chat website means handing that document to a third party - and if the project is under NDA, or your IT department reviews every tool that touches project data, that is not a gray area. It is a no.
So most designers quietly pick one of two bad options: use AI and hope nobody asks where the schema went, or skip AI and draw everything by hand. There is a third option: BYOK in a desktop ERD tool, where every AI request travels straight from your machine to your own OpenAI, Claude, Gemini, or DeepSeek key - no vendor server in between.
