While fog is not a major issue, smog can be - November to January is often the peak for air pollution related issues in the north and air quality in the NCR and surroundings (Agra more than Jaipur) is generally poor. If you have breathing/respiratory issues (such as asthma or chronic bronchitis) I would not recommend it.
Check AQI readings here:
https://app.cpcbccr.com/AQI_India/ or here:
https://aqicn.org/map/india/