It's determined by who takes the balls to the tournament desk.

No, it's not! It's based on skills and performance!
Rating Number
Description
1.0
Just starting tennis. Essentially, someone stepping on the court for their first lesson.
1.5
A player with limited experience. This player is working on basic stroke production trying to keep a ball in play.
2.0
This player knows how to hit all of the strokes, but lacks court experience. They are familiar with the basic court positions for singles and doubles.
2.5
This player is learning to judge where the ball is going although court coverage is weak.They can sustain a short rally of slow pace. Beginner: This is the lowest rating level for which the USTA offers League play.
3.0
This player is consistent when hitting medium paced shots, but they are not comfortable with all strokes. This player's shots lack directional control and power.
3.5
This player has achieved dependable stroke production with directional control on moderate paced shots. They still lack depth and variety. This player is starting to show team work in doubles. This ranking is considered intermediate level.
4.0
This player has very dependable strokes including directional and depth control on both the forehand and backhand sides. This player can use ground strokes, volleys, lobs, overheads, and approach shots with success. This player occasionally forces errors. Rallies are often lost due to impatience. This player shows strong teamwork in doubles. High Intermediate. This is the bell curve in USTA league tennis.
4.5
In addition to directional and depth control, this player has begun to master the use of varying spin and power. This player can handle considerable pace and shows sound footwork. They can vary their game plan according to opponents. They can vary their serve and have placement of their second serve. This player tends to over hit on difficult shots. In addition to sound doubles team work, this player often shows aggressive net play. This is the beginning of the advanced ratings.
5.0
This player shows shot anticipation and often has an outstanding shot or attribute around which their game may be structured. This player can regularly force errors and hit winners from short balls. In addition to power and placement, this player can spin and place second serves.
5.5
This player has developed power and consistency as a major weapon. This player can vary strategies and styles of play in competitive situations and hits dependable shots when under pressure or stress.
6.0, 6.5, & 7.0
These players have intensive training for National programs or the Pro tour. They have National or Sectional ratings. Some have International rankings. In short, professionals.