The Visa free entry is based on certain criteria to be ensured by the  tourist. Complete details are provided in the official website ( link attached below). The following may be required, a prior and confirmed hotel booking, health insurance in Oman, a return ticket and passport validity of at least 6 months. 

To check the details and the eligibility, its advisable to visit the official site of the Omani e-visa, before applying for the visa and planning your trip. 

Link  - 

Omani Visa Eligibility Wizard

Know Your Visa Type