In addition to some sellers peddling FAKES out there, there are a number of additional obvious and not-so-obvious things to look for in the ad. If the information is missing, it's best to just ask the seller for more details before bidding.   Here are some things I look for (I have been collecting dolls all my life and specifically French Poupees and Bebes since I was 17. I am not almost 50, so that is over 30 years. Many of these things modify the value of the doll slightly.
1. Is wig original to the doll, antique but not original, or a replacement new wig. What is wig material? Many times the ad will say "mohair wig" and nothing else.
2. Is the pate original or at least antique, or a newer replacement? Pates are often not even mentioned in many ads.
3. Have sleep eyes been reset and fixed so as not to move? Are fixed eyes reset? Does Steiner lever eye mechanism work? Many ads do not mention the eyes except the color.
4. Is the body the right size and type for the doll, is it an appropriate antique, does it have any repainting, repairs or replacement parts?
5. Is all the clothing original to the doll, antique, replacements of antique fabrics or replacements with new fabrics. Are there any synthetic materials used anywhere in the clothing - in the ribbons, decorative flowers, etc ?  Often ads will say the outfit is of say jacquard silk but does not say that the dress or the fabric itself is antique. It can be disappointing if you paid more for an antique dress but ended up with a new one. Ask for a pic of the fastenings. Most old outfits will not have snap closures.
6. Are the socks antique or new (cotton or rayon), are the shoes original to the doll, era or model, are they antique and at least French not German, are the shoes marked on the bottoms, are the soles or ribbons replaced? There are some excellent reproduction shoemakers out there whose work is very difficult to distinguish from antique models, especially when seen in a web quality photo.
7. Does the doll have Provenance (history of ownership including the original owner) 
8. If the seller advertizes as a member of NADDA of UFDC or has very high feedback and positive percent feedback, you will usually be OK.  Be wary of sellers with low feedback count, zero feedback count and shipping address outside the US or Canada.
I hope this helps.