Struct McpClientHandler 

pub struct McpClientHandler { /* private fields */ }

Available on crate feature rmcp only.

An MCP client handler that automatically re-fetches the tool list when the server sends a notifications/tools/list_changed notification.

This handler implements rmcp::ClientHandler and bridges the MCP notification lifecycle with Rig’s ToolServer. When the MCP server’s available tools change, this handler:

1. Removes previously registered MCP tools from the tool server
2. Re-fetches the full tool list from the MCP server
3. Registers the updated tools with the tool server

Usage

Use McpClientHandler::connect for a streamlined setup that handles connection, initial tool fetch, and registration in one call:

let tool_server_handle = ToolServer::new().run();
let handler = McpClientHandler::new(client_info, tool_server_handle.clone());
let mcp_service = handler.connect(transport).await?;

The returned RunningService keeps the MCP connection alive. When the server updates its tools, the handler automatically syncs with the tool server.

Implementations

impl McpClientHandler

pub fn new( client_info: ClientInfo, tool_server_handle: ToolServerHandle, ) -> Self

Create a new handler with the given client info and tool server handle.

The tool_server_handle should be a clone of the handle used by the agent, so that tool updates are reflected in agent requests.

pub async fn connect<T, E, A>( self, transport: T, ) -> Result<RunningService<RoleClient, Self>, McpClientError>

where T: IntoTransport<RoleClient, E, A>, E: Error + Send + Sync + 'static,

Connect to an MCP server, fetch the initial tool list, and register all tools with the tool server.

Returns the running MCP service. The connection stays alive as long as the returned RunningService is held. When the server sends notifications/tools/list_changed, this handler automatically re-fetches and re-registers tools.

Errors

Returns McpClientError if the connection fails, the initial tool fetch fails, or tool registration with the tool server fails.

Trait Implementations

impl ClientHandler for McpClientHandler

fn get_info(&self) -> ClientInfo

async fn on_tool_list_changed(&self, context: NotificationContext<RoleClient>)

fn ping( &self, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<(), ErrorData>> + Send

fn create_message( &self, params: CreateMessageRequestParams, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<CreateMessageResult, ErrorData>> + Send

fn list_roots( &self, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<ListRootsResult, ErrorData>> + Send

fn create_elicitation( &self, request: CreateElicitationRequestParams, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<CreateElicitationResult, ErrorData>> + Send

Handle an elicitation request from a server asking for user input.

fn on_custom_request( &self, request: CustomRequest, context: RequestContext<RoleClient>, ) -> impl Future<Output = Result<CustomResult, ErrorData>> + Send

fn on_cancelled( &self, params: CancelledNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + Send

fn on_progress( &self, params: ProgressNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + Send

fn on_logging_message( &self, params: LoggingMessageNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + Send

fn on_resource_updated( &self, params: ResourceUpdatedNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + Send

fn on_resource_list_changed( &self, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + Send

fn on_prompt_list_changed( &self, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + Send

fn on_url_elicitation_notification_complete( &self, params: ElicitationResponseNotificationParam, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + Send

fn on_custom_notification( &self, notification: CustomNotification, context: NotificationContext<RoleClient>, ) -> impl Future<Output = ()> + Send