It depends upon the language in the listing agreement you have with your agent's brokerage. In many State or Board provided listing contracts, you agree to conduct all business and communications through solely through your agent. Aside from this, there is not likely anything that would disallow you to do this, as nobody other than your agent would have a possible claim against you (and it is unlikely he or she would take action against you). Regardless, this is absolutely a conversation you should have with your agent before doing anything. Hopefully you are functioning well as a partnership in the process of getting you a new home. If this house is still available or for future reference, you could discuss with your agent about making your letter an attachment to be part of the offer to purchase. That way, the listing agent is compelled to show it to the seller.
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