I think if you just keep it simple and calm, you'll get a friendly response.  The majority don't seem to have an issue with it, so I suspect you're going to find no problem overall.

briefly describe yourself (many people generally do this to some extent) in your intro email and if she's got a problem with it she will either let you know directly or perhaps not reply at all.

And I've not had one single negative experience to report. But I also trend toward providers at a higher price point, so you may want to take that into consideration. FWIW, the only local ladies I see expressing racial preferences in their adverts are at the low end of the spectrum and aren't worth getting inside of anyway. Which is somewhat ironic. Anyway, if you'd rather ask, I wouldn't fret over the phrasing of the question if I were you. I don't think any reasonable provider would be offended at you inquiring. You could simply say "do you entertain black gentlemen?" and leave it at that. Have fun.

Why don't you just give her your TER ID as part of the request?  That will be a huge clue to her if she's the type that it would be an issue for.

I have run into a situation where a provider's preference not to meet black clients was never stated.  The provider informed me, at the door, that she didn't date black men.. I was sent walking!  ...not a good feeling.  

Since then, I simply give an accurate description of myself; that seem to help a lot.  Sometimes, a quick chat on the phone will allow the provider a chance to "get a feel" of things as well.  Again, being sure to ask if she is comfy dating black men.

It's All In The Delivery

I am an Atlanta provider and I would say that it's all in a gentleman's delivery.  If you call and are well spoken, kind, friendly and gives us the details we are looking for you will have no problem scheduling an appointment (in my opinion) even if we can tell your race over the phone.  If you hit us with the "hey baby what's up" upon us answering the phone or you are overly graphic in scheduling a first time appointment you might be declined---and this goes for gentlemen of ALL races.

Many Black men are declined for numerous reasons (1. what they are packing can be too much for some. 2. Rudeness, lack of professionalism or too graphic. 3. (2nd appt request) It's not a date but a straight hard core bang session.)  Please forgive my bluntness but those are the reasons I have declined and other girls I know have declined.  Race doesn't matter...it's all in the delivery.  You are also welcome to get in a little practice with me 404-771-7574.

... but I've never thought to express my race ahead of time. I guess I figure that if there's a problem, I'll find out at the door. Occasionally during small talk I'll mix in a "So, do you see a lot of white guys?" Just for curiosity sake.  But I always work under the assumption that green is the only color of importance.

I might simply say something like the following.  "To ensure we both have a great time do you have any age or ethnic preferences"