# AIP012 — unused-template-variable
**Category:** clarity **Severity:** warning
## What
Detects template variables (like `{variable}` or `{{ variable }}`) that are never interpolated or substituted in the prompt.
## Why it matters
Unused template variables indicate incomplete or dead code in a prompt template. They either suggest a missing substitution step or a forgotten variable definition.
## Example
```
Hello, {name}!
The date is {date}.
```
If the code only ever substitutes `{name}` and never `{date}`, the latter is unused.
## Fix
Remove unused variables or ensure they are properly substituted:
```
Hello, {name}!
```
## Autofix
This rule includes a safe autofix that removes unused template placeholders.