Combine chicken, celery, mayonnaise, onion, parsley, pesto, salt, and pepper in a bowl. Serve right away with cherry tomatoes or over sliced tomatoes (optional) or refrigerate in an airtight container for up to 3 days.
In order to calculate Net Carbs of any whole food item, it's a simple calculation based on the Nutrition Facts panel:
Total Carbohydrates - (Minus) Dietary Fiber = (Equals) Net Carbs
For low carb products sweetened with sugar alcohols (ie: glycerin, maltitol, etc), refer to the Nutrition Facts panel of the product:
Total Carbohydrates - (Minus) Dietary Fiber - (Minus) Sugar alcohol = Net carbs
This reflects the fact that Dietary Fiber doesn't impact blood sugar levels. Sugar alcohols also have a negligible impact on blood sugar, they too are subtracted from total carbs to yield the Net Carb count.