Generating OpenAPI doc with Utoipa + Scalar + Axum in Rust

Cargo.toml

[package]
name = "utoipa_scalar_example"
version = "0.1.0"
edition = "2024"

[dependencies]
axum = "0.7"
tokio = { version = "1", features = ["full"] }
utoipa = { version = "4", features = ["axum_extras"] }
utoipa-swagger-ui = "5"
utoipa-scalar = { version = "0.1", features = ["axum"] } 
serde = { version = "1", features = ["derive"] }

main.rs

use axum::{Json, Router, routing::get};
use serde::{Deserialize, Serialize};
use tokio::net::TcpListener;
use utoipa::OpenApi;
use utoipa_scalar::Scalar;

#[derive(Serialize, Deserialize, utoipa::ToSchema)]
struct HelloResponse {
    message: String,
}

#[utoipa::path(
    get,
    path = "/hello",
    responses((status = 200, body = HelloResponse))
)]
async fn hello() -> Json<HelloResponse> {
    Json(HelloResponse {
        message: "Hello from Scalar!".to_string(),
    })
}

#[derive(OpenApi)]
#[openapi(paths(hello), components(schemas(HelloResponse)))]
struct ApiDoc;

#[tokio::main]
async fn main() {
    let app = Router::new()
        .route("/hello", get(hello))
        .nest("/scalar", Scalar::new(ApiDoc::openapi()).into());

    let listener = TcpListener::bind("0.0.0.0:3000").await.unwrap();

    println!("→ Open http://localhost:3000/scalar");

    axum::serve(listener, app).await.unwrap();
}

Result