---
title: reference
framework: evaluations
role: symbol
role_heading: Instance Property
path: evaluations/modeljudgeprompt/reference
---

# reference

An optional closure that provides labeled reference data to include in the model-as-judge prompt.

## Declaration

```swift
let reference: (nonisolated(nonsending) @Sendable (Input, Input.ExpectedValue) async throws -> [String : String])?
```

## Discussion

Discussion The closure receives both the input sample and the model’s response, allowing reference data derived from either, for example, running a grammar checker on the response, or passing the sample’s expected value for comparison.

## See Also

### Customizing judge input

- [instructions](evaluations/modeljudgeprompt/instructions.md)
- [evaluationTarget](evaluations/modeljudgeprompt/evaluationtarget.md)