A creator partnership usually starts with a friendly message and a free product. That works until the post goes up three weeks late, says something you wouldn't, and can't be reused on your own account.
1. What they'll make
Say how many posts, in which formats, on which platforms. One reel and three stories is an agreement. Some content is not.
2. When it goes live
Give a date, and say whether you want to see the post first. Most creators are happy to share a draft if you ask at the start rather than the day before.
3. What it has to say
List the two or three things that must be right: the product name, the offer, the link. Leave the rest to them. Their audience follows them for their voice, not yours.
4. How it's disclosed
A paid or gifted post has to say so. Agree the wording and where it goes, so nobody is guessing.
5. Whether you can reuse it
If you want to run their video on your own account, say so and agree for how long. It is the thing most often left out.
For a small collaboration, all of this fits in one clear message that both sides reply yes to. The point is that it's written down.