Many here are replying in regards to an Emotional Support Animal.
To be succinct...
An emotional support animal is NOT the same as a service animal.
They are two different categories of animals, with two different purposes, and as such, with the exception of New York and California, fall under two different sets of rules.
A guest with a service animal does NOT have to disclose to the just that the service animal is accompanying them, and a host may not deny a guest because of their service animal, or provide differential treatment in any way. A host also MAY NOT charge extra fees, animal fees, or any additional fees because of a service animal.
The host MAY ask if the service animal is necessary because of a disability and which services that they are trained to perform.
The host MAY NOT ask to see them perform the service or really anything further than what I've mentioned above.
Again, an ESA is different than a SERVICE animal, is NOT considered a pet, and does NOT have to be disclosed AT ALL (but it is encouraged for the sake of transparency).