Fur-N-Fowl
Fluffy Dinosaur Breeder
That's pretty much exactly what mine will say, but with more detail. Such as:
-You, the buyer, agree to pay attention to the health of any birds you recieve from me and to treat them by any means within your power to do so. I, the seller, am not responsible for the death of any birds bought from me due to lack of proper husbrandy practices on your property.
-The buyer agrees to quarantine any live poultry bought from me for a minimum of 2 weeks out of direct content with any existing flocks. The quarantined birds will have access to fresh food and water. Sterile equipment and proper biosecurity measures will be used during quarantine to prevent the spread of disease. The seller is not responsible for any disease or harm that is caused by the buyer not following a proper quarantine procedure.
-The buyer hereby signifies that the poultry they purchased from (insert farm name) were visibly and certifiably healthy upon receipt.
And so on
Yep, pretty much the same just different wording!
I'm glad you are doing that too though and I'm not the 'only one'

There is a lot of people here that get their birds, even young chicks and just throw them in with their own flock. A huge risk to illness spreading and also the new chicks being pecked and killed.
I've stated on my agreement that the buyer has fully checked over the bird and is happy with its physical health at the time of purchase like you have!
I'm not a business but I still think it's worthy of doing in the long run even though I am just a hobby breeder.