eBay uses a simple script to check listings for contact information. Anything that looks like it might be a phone number or an email address can trigger that warning. And because scammers try various tricks to get around the block, eBay has to block things that might be obscured phone numbers or email addresses as well.
Try deleting anything with an "@" symbol from the item description, or any numbers that might look like phone numbers to a simple scanning script.
