Trader/Barterer

Having worked with tradesmen, merchants, and/or negotiators, you have the necessary knowledge to recognize when you are at a disadvantage or advantage during a negotiation, and can easily barter with inexperienced individuals (most peasants, commoners, etc.) without hindrance (must still work for it regarding shopkeepers however). If one with this skill chooses to barter or negotiate with another skilled in this trade, such as merchants and ambassadors, a charisma roll must be made as the negotiations progress. Those with the etiquette proficiency will have an additional +1 to their charisma check.

Characters who grew up as an apprentice under, assistant to, or who practiced the works of tradesmen, merchants and/or negotiators, will have the chance to have this particular Extra Skill. For it pertains to Empathetic Intelligence and Awareness, Basic Etiquette, Clear Communication, Control of the Conversation, Persuasion and Negotiation. Thus while the character never has to be the one actually engaging in trades, selling, business and/or negotiations, they do need to have been exposed to the process for long periods of time. This time would need to be vastly longer if the character is learning on their own without a mentor.
With the knowledge and experience of a tradesman under their belt, characters with this skill can expertly identify most wording structures and patterns, facial expressions and emotional cues, subtle cues and hints, and so forth. This could result in identifying their level of engagement with you or if they are distracted, tone of voice and their emotional state, hidden meanings behind their words, whether they are attempting to confuse or outmaneuver you, and so forth. In addition, should one with this skill engage in negotiations or haggling with others, they know the right wording, tone, expression and amount of engagement to increase their chances, even against another tradesman in the same profession (unless emotionally compromised).
Furthermore the character with this skill can attempt to use their knowledge of social cues, expressions, body signs, tone, inflections and more to attempt to identify any deception, nervousness or anxiety, or other subtle or hidden emotions that the individual may be attempting to keep under the surface. This reading is automatic with unskilled individuals. However when reading those who are skilled at keeping themselves concealed, an intelligence check must be made with a modifier ranging from -2 to +2 depending on the individual's skill. The information gained is usually just small information rather than full information. Example: One could note that a merchant is hiding something about what they're trying to sell, but no hints as to what that might be, if it's with ill intent or just embarrassment, etc. Or a nobleman seems a bit too anxious when speaking of a particular subject, but not if it's out of fear, or if they know something about it they don't want revealed. Or a guardsman reacts a bit smugly in a subtle reaction to a decision made, but not if they think it's funny, or if they have something malicious in mind with that knowledge.