Let’s look at important things here –
Mercury - Mercury represents communication skills, marketing, calculative ability, younger siblings, hobbies, skills with hands, intelligence, quick decision making, logical thinking, youthfulness etc.
Swati - Swati is nakshatra of independence, Justice, Fair-Play and Business People. For more information on Swati Nakshatra, please check this link - https://www.astrosaxena.com/swanaksh .
Libra - As Swati is a part of Libra, Libra sign and its representations also become important. Libra is the 7th sign of Zodiac Belt, hence it represents the energy and things related with 7th house of horoscope, i.e. Market Place, Business, Partnerships, Relations etc. Libra is sign of Balance, i.e. striking the Balance between 2 parties/ideologies or even at personal level between our own dilemmas. It is sign of Peace and Diplomacy. And this is what we are seriously looking for after the conflicts and disagreements of Virgo, i.e. Peace to prevail. At personal level, Libra is seen as sign of Relationships. Libra is consisted of 2 and half Nakshatra named Chitra, Swati and Vishakha. Libra's lord is Venus only.
Rahu - As Rahu rules Swati, Rahu's position and dignity is important to know about the overall functioning of any planet in Swati.
Venus - As Venus rules Libra, Venus position and dignity is important to know about the overall functioning of any planet in Swati.
Houses Involved – Also, we can’t afford to forget the houses involved as a planet can be ruling different houses and sitting in different house for every person as per ascendant and planet’s position. To know overall affect, we have to consider the houses involved as those areas of life are being impacted.
Interpretation of Mercury in Swati Nakshatra – Mercury is here in friendly sign. Hence, dignity-wise it is very strong. The common themes around Mercury, Libra and Swati is that all of them represent business. So, this position can certainly make someone inclined towards business and work independently. They can be very shrewd business person too. Their business would largely be communication or counselling/teaching/consulting based. They can have a pleasant way of communicating too. They can be seen as independent individuals. But same individualistic approach can become an issue in relationship matters if Mercury is relationship oriented planet for you. They can be too liberal and may see relationship as a matter of bondage for them. So, this position can be good for business setup career but may not be too good for relationship matters
Role of Rahu – Rahu placement is important to guide Mercury in right direction, being Swati's lord.
Role of Venus - Likewise, Venus placement is important to guide Mercury in right direction, being Libra lord.
Other Factors – And of course, we need to consider conjunction, aspects, house lordship, house position and dashas etc to know the exact results of Mercury in Swati. So, we always need to take a holistic view of chart rather than just 1 planetary position.
Conclusion – So, this is how I see Mercury in Swati can work in a chart.