Some features that are irrelevant to whether or not something is classified as mediated reinforcement include whether or not the stimulus is conditioned or unconditioned, the type of receptor affected by the stimulus change, and any evocative or eliciting effects of the stimulus change.
A stimulus change that has the following features:
It occurs after a response has been emitted
It increases the future probability of that response
It results from the action of another individual
Formal and dynamic features of the response
Formal and dynamic features of the controlling variable
Whether or not the current response is reinforced
The “meaning” of either the stimulus or the response