How to compensate an agent on a build to suit deal

[Chad Lubke]

I met with an agent and her clients yesterday and today and a spec home we have for sale. They really liked the house but want to have a similar home built on another lot I own in the same community that has better views. The lot I own just has a sign on it with my logo and says "Coming Soon", no marketing, or MLS listing, etc. Total amount I have into the lot is $140k, the total package, house and lot will be around $850k. There has been nothing in writing yet, just a verbal discussion. I am wondering how do I craftfully get her to just get commission on the land, or is that implied since there is no listing...