ClientHandler Trait

ClientHandler provides default implementations for all incoming requests from the server. Override only the methods you need.

Key Methods

#[async_trait]
pub trait ClientHandler: Send + Sync + 'static {
    // Requests from server
    async fn handle_ping_request(
        &self, params: Option<RequestParams>, runtime: &dyn McpClient,
    ) -> Result<Result, RpcError>;

    async fn handle_create_message_request(
        &self, params: CreateMessageRequestParams, runtime: &dyn McpClient,
    ) -> Result<CreateMessageResult, RpcError>;

    async fn handle_list_roots_request(
        &self, params: Option<RequestParams>, runtime: &dyn McpClient,
    ) -> Result<ListRootsResult, RpcError>;

    async fn handle_elicit_request(
        &self, params: ElicitRequestParams, runtime: &dyn McpClient,
    ) -> Result<ElicitResult, RpcError>;

    async fn handle_get_task_request(
        &self, params: GetTaskParams, runtime: &dyn McpClient,
    ) -> Result<GetTaskResult, RpcError>;

    async fn handle_cancel_task_request(
        &self, params: CancelTaskParams, runtime: &dyn McpClient,
    ) -> Result<CancelTaskResult, RpcError>;

    // Notifications from server
    async fn handle_resource_updated_notification(
        &self, params: ResourceUpdatedNotificationParams, runtime: &dyn McpClient,
    ) -> Result<(), RpcError>;
    async fn handle_resource_list_changed_notification(
        &self, params: Option<NotificationParams>, runtime: &dyn McpClient,
    ) -> Result<(), RpcError>;
    async fn handle_prompt_list_changed_notification(
        &self, params: Option<NotificationParams>, runtime: &dyn McpClient,
    ) -> Result<(), RpcError>;
    async fn handle_tool_list_changed_notification(
        &self, params: Option<NotificationParams>, runtime: &dyn McpClient,
    ) -> Result<(), RpcError>;
    async fn handle_logging_message_notification(
        &self, params: LoggingMessageNotificationParams, runtime: &dyn McpClient,
    ) -> Result<(), RpcError>;
    async fn handle_progress_notification(
        &self, params: ProgressNotificationParams, runtime: &dyn McpClient,
    ) -> Result<(), RpcError>;
    async fn handle_cancelled_notification(
        &self, params: CancelledNotificationParams, runtime: &dyn McpClient,
    ) -> Result<(), RpcError>;
    async fn handle_task_status_notification(
        &self, params: TaskStatusNotificationParams, runtime: &dyn McpClient,
    ) -> Result<(), RpcError>;

    // Custom request handler
    async fn handle_custom_request(
        &self, request: CustomRequest, runtime: &dyn McpClient,
    ) -> Result<ListRootsResult, RpcError>;
}

Basic Client

pub struct MyClientHandler;
#[async_trait]
impl ClientHandler for MyClientHandler {}

All methods return sensible defaults or error responses, so the minimal client just needs an empty impl.