It would be good to be able to specify an experience level by species (pre-defined experience levels) both in a sitting request and for the sitters. For example: I have horses and need a sitter who knows how to be safe in handling them - not just someone who has ridden or petted one before. Pet owners who have a dog or cat that has a health issue will need a sitter that is comfortable giving medication, and so on.
Perhaps there could be pre-defined experience categories to reference, such as:
0: no or negligible experience with species
1: I am comfortable with this species (some interaction in the past; not anxious about it)
2: I have lived with or previously cared for this species for a significant amount of time and know how to handle them safely on a lead (if dog or horse)
3: I know how to give minor medical care (oral medications, ointments) to this species
4. I am very experienced with this species and can manage more complex health care issues.