# XO0424: a wire string for a format the struct does not derive

`json "..."` names a field for `derive Json`, `sql "..."` for `derive SqlRow`, and `xml "..."` for `derive Xml`. On a struct without that derive the string changes nothing, which is likely a mistake. Add the derive, or remove the string. See core 2.2 and decision 0315.

## Example

```xo
struct Row {
  created sql "created_at": Int
} derive Json
```

## Fix

```xo
struct Row {
  created sql "created_at": Int
} derive Json, SqlRow
```

Run `xo explain XO0424` for this text in a terminal, or see
[section 10.6 of the specification](../../spec/core/#106-diagnostic-codes).