In MLS but Option?

If you had a seller who is willing to give you an option or purchase contract and it’s only on the mls is that ‘tortious interference’?

Or does there have to be a specific listing agreement with a realtor? Thanks

it depends what their listing agreement type and contract states. if they have a limited agency agreement you may be fine. if they have an exclusive right to sell, they are obligated to fulfill the contractual agreement they entered into and you should not bypass listing agent.