Attribute Macro openapi 

#[openapi]

Declares OpenAPI metadata for a controller route method.

#[openapi] is valid only on methods inside a #[routes] impl block. It is metadata-only behavior: it does not change request execution, but it enriches the RouteMetadata emitted by #[routes] so CLI and OpenAPI builders can generate useful documentation.

Basic syntax:

#[routes]
impl UsersController {
    #[get("/:id")]
    #[openapi(
        summary = "Fetch a user by id",
        tags = ["users"],
        status = 200,
        response = UserDto,
    )]
    async fn show(&self, Path(id): Path<String>) -> Json<UserDto> {
        Json(self.service.find(id).await)
    }
}

Supported metadata includes summaries, tags, status codes, request schemas, and response schemas. DTO schema names are recorded for tooling; they do not serialize or validate requests at runtime. Common errors include missing summary, non-string tags, invalid status values, duplicate metadata, or placing the attribute outside a route method.