Best practice in advertising animal sales is set out on the RSPCA website here: https://kb.rspca.org.au/wp-content/uploads/2019/03/RSPCA-GUIDE-Online-Sale-of-Pets.pdf
It includes items such as:
1. Stating the status of the seller - are you a breeder, a shelter, a rescue group, or an individual?
2. How old is the animal?
3. The gender of the animal.
4. Contact details: Phone number, email etc
5. Location of animal.
6. Type of animal.
7. Microchip number if applicable.
8. Desexed or entire.
9. Expected adult size.
10. Vaccination status if applicable.
11. Health status.
12. Breeder registration number if application.
13. Care information for the buyer.