Metric Glossary
A metric is the thing a rule measures. This page explains the ones you'll use most. The tool has more — the same descriptions appear in the in-app Metric Glossary panel, and every column header in the results table has a tooltip.
Most metrics are a percentage: how often something happened out of the times it could have. Higher is usually better, except where noted.
In the right sidebar, the Metric Glossary panel lists metrics with their short code. Click any one to expand its description; a metric where lower is better says so in amber. Use Show all to reveal the full list and Show less to collapse it. Metrics used in your current rules float to the top.
Serve
| Metric | What it measures |
|---|---|
| Service Hold % | Share of the player's own service games they won. |
| Service Pts W% | Share of points won on their own serve. |
| 1st Serve Pts W% | Share of first-serve points won. |
| 2nd Serve Pts W% | Share of second-serve points won. |
| 1st Serve % | Share of first serves that landed in. |
| BP Save % | Share of break points saved (a point that, if lost, loses the game). |
Return
| Metric | What it measures |
|---|---|
| Return Pts W% | Share of points won on the opponent's serve. |
| Return Games W% | Share of games won on the opponent's serve. |
| Break Pt W% | Share of break points converted. |
| Opp Hold % | How often opponents held their serve. Lower is better here. |
Match scenarios
These count how often a specific in-match situation happened — useful for finding players with a particular temperament.
| Metric | What it measures |
|---|---|
| Win first set % | How often the player won the opening set. |
| Won set 1, won match | How often winning set one led to winning the match. |
| Lost set 1, won match | Comeback wins after dropping the first set. |
| Hold serve at 5-4 | Serving out the set at 5-4 and winning it. |
| Tie Breaks % | Share of tie breaks won. |
Lower is better for a few metrics — like Opp Hold % or Immediately broken back. The tool knows the difference, but keep it in mind when choosing an operator.
Reading a metric in a rule
Put together, a metric becomes a plain-English condition:
Return Games W% is greater than 35.
See Build a Rule for how to turn these into a system.
Tips
| Tip | Why it matters |
|---|---|
| Hover a glossary metric for more | Expanded text in the sidebar often clarifies edge cases. |
| Watch the (lower is better) flag | It flips how you think about the threshold — Opp Hold % < 30 is stricter than RGW > 30. |
| Mix serve and return metrics | Players often have an edge on one side; combining them is rare and powerful. |
| Match scenarios are rare | Metrics like "Win set 1, win match" happen in only a small slice of matches — use with caution. |