you are in the room and the gift has been taken care of.

However, there is no law against touching or kissing or fondling someone's feet that I know of, so it may be OK to suggest this when contacting a provider.

I know some providers are pretty tickelish when it comes to feet, so if this is what turns you on, then by all means you should inquire.

By the way, I love feet too.

Especially if you're totally new to the hobby (and not just new to a particular provider) it's generally accepted that anything related to the intimate part of the encounter is best discussed only after you have actually met privately with one another at the location. Asking about something related to the sexual act on the phone even using euphemisms especially when the provider is unfamiliar with you is a great way to make her uncomfortable or skeptical and get hung up on.
Even if it's "just" a foot fetish, saying its a fetish usually implies sexual contact so I wouldn't ask about it until the appointment time for discretion's sake. It may be okay to ask in an email for some providers but don't take it as a matter of course. Most will only want to talk about screening, rates, time, location, and wardrobe requests at most over phone or email.
If you're new make sure you read the newbie FAQs and if you have a particular thing you're into sift through a lot of reviews beforehand to see if a lady has done what you prefer before. That might save you the awkwardness of having to ask beforehand.