Here's a truth that reorders how you practice: a serve can only be as consistent as the toss it's built on. If the ball lands in a slightly different spot every time, your swing has to improvise every time — a little later here, a reach-back there — and a swing that improvises can't groove. Most "my serve is so streaky" problems are toss problems wearing a swing costume.
The toss is a platform, not a flourish
Think of the toss as laying a ball onto an invisible shelf in the sky and letting it hang there for you to hit. The whole serve stands on that shelf. When the shelf is in the same place every time, the swing gets to repeat the exact same motion, and repetition is where reliability comes from. When the shelf wanders — a bit left, a bit low, a bit behind — the serve becomes a series of different serves that happen to share a name.
What makes a toss repeat is boring and mechanical: the same arm path, a straight arm, a release off the fingertips (not a flick from the palm), and letting go at the same height every time. Boring is the goal. You want a toss so dull it never surprises you.
What the camera can — and can't — tell you
Honesty first, because it changes how you read your feedback: the tracker cannot see the ball. There are no keypoints on it. So CoachVision never tells you where the ball went, how high it flew, or that it drifted behind you — those would be inventions.
What it does read is your tossing arm: how high it reaches at its peak, and whether it stays long. A tall, full toss-arm reach is the platform the serve stands on; a low one is the arm quitting early or bending at release, and a bending release is the single most common source of a scattering toss. So while the app can't grade the ball's landing spot, it can tell you whether your tossing arm is doing the repeatable thing — which is the part you actually control.
The fix — Toss-and-Catch Drill
You don't need to serve to fix a toss. In fact, taking the swing away is the point.
Lay a racquet flat on the court at about one o'clock, just inside where you stand, on your tossing side. Toss the ball and — without swinging — let it drop. It should land on the strings. Reset and repeat. You're training the arm to deliver the ball to the same shelf every single time, with the swing removed so nothing distracts you from the one job. Straight arm, fingertip release, catch-height toss.
Twenty tosses, aiming for fifteen or more on the strings. Do it as a warm-up before you ever hit a serve. As the arm learns the groove, the ball stops wandering — and your swing, finally handed the same platform every time, gets to become one repeatable motion instead of twenty different ones.
Then film a serve side-on and watch your toss-arm reach settle into the same tall number, serve after serve. A repeatable arm is a repeatable toss, and a repeatable toss is the quiet foundation under every reliable serve in the game.