You need your vendors and suppliers in order to serve your customers. If your care about your customers, you must care about your suppliers. They are there to help you deliver the value you've promised. And you need to approach them with that mindset.

They're not your employees. They are other business owners. Which means you are their customer.

You can help them understand what is valuable for you as their customer. You can help lay out the expectation to make their job of discovery easier.

There are 2 ways you do this.