JSON deserialization not working in Jetpack Compose

To decode (deserialize) JSON data in Jetpack Compose seems quite simple, however I’ve encountered a problem that I can’t solve. I’m using the latest version of Android Studio and I’m not sure whether the .decodeFromString() function works in AS or I should use IntelliJ IDEA for this? Here’s my code:

dependencies {
    implementation(libs.kotlinx.serialization.json)
}

import kotlinx.serialization.ExperimentalSerializationApi
import kotlinx.serialization.Serializable
import kotlinx.serialization.decodeFromString
import kotlinx.serialization.json.Json

@ExperimentalSerializationApi
class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        enableEdgeToEdge()
        setContent {
            JSONsibleTheme {
                DecodedText()
            }
        }
    }
}

@Serializable
data class User(val id: Int, val name: String)

@ExperimentalSerializationApi
@Composable
fun DecodedText() {
    val jsonString = """
    {
        "id": 722549,
        "name": "John Smith"
    }
    """
    val deserialized = Json.decodeFromString<User>(string = jsonString)
    Text(
        text = "${deserialized.name}, ${deserialized.id}"
    )
}

I can’t run this code either on a simulator or a real device because the @Serializable annotation doesn’t apply (it’s underlined in yellow). The Warning says:

// kotlinx.serialization compiler plugin is not 
// applied to the module, so this annotation would 
// not be processed. Make sure that you've setup 
// your buildscript correctly and re-import project.