Trait ServerHandler 

pub trait ServerHandler:
    Sized
    + Send
    + Sync
    + 'static {
    // Provided methods
    fn ping(
        &self,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture { ... }
    fn initialize(
        &self,
        request: InitializeRequestParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<InitializeResult, ErrorData>> + MaybeSendFuture { ... }
    fn supported_protocol_versions(&self) -> Cow<'static, [ProtocolVersion]> { ... }
    fn discover(
        &self,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<DiscoverResult, ErrorData>> + MaybeSendFuture { ... }
    fn complete(
        &self,
        request: CompleteRequestParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<CompleteResult, ErrorData>> + MaybeSendFuture { ... }
    fn set_level(
        &self,
        request: SetLevelRequestParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture { ... }
    fn get_prompt(
        &self,
        request: GetPromptRequestParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<GetPromptResponse, ErrorData>> + MaybeSendFuture { ... }
    fn list_prompts(
        &self,
        request: Option<PaginatedRequestParams>,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<ListPromptsResult, ErrorData>> + MaybeSendFuture { ... }
    fn list_resources(
        &self,
        request: Option<PaginatedRequestParams>,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<ListResourcesResult, ErrorData>> + MaybeSendFuture { ... }
    fn list_resource_templates(
        &self,
        request: Option<PaginatedRequestParams>,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<ListResourceTemplatesResult, ErrorData>> + MaybeSendFuture { ... }
    fn read_resource(
        &self,
        request: ReadResourceRequestParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<ReadResourceResponse, ErrorData>> + MaybeSendFuture { ... }
    fn accepted_subscription_filter(
        &self,
        requested: &SubscriptionFilter,
    ) -> Option<SubscriptionFilter> { ... }
    fn listen(
        &self,
        context: SubscriptionContext,
    ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture { ... }
    fn subscribe(
        &self,
        request: SubscribeRequestParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture { ... }
    fn unsubscribe(
        &self,
        request: UnsubscribeRequestParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture { ... }
    fn call_tool(
        &self,
        request: CallToolRequestParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<CallToolResponse, ErrorData>> + MaybeSendFuture { ... }
    fn list_tools(
        &self,
        request: Option<PaginatedRequestParams>,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<ListToolsResult, ErrorData>> + MaybeSendFuture { ... }
    fn get_tool(&self, _name: &str) -> Option<Tool> { ... }
    fn on_custom_request(
        &self,
        request: CustomRequest,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<CustomResult, ErrorData>> + MaybeSendFuture { ... }
    fn on_cancelled(
        &self,
        notification: CancelledNotificationParam,
        context: NotificationContext<RoleServer>,
    ) -> impl Future<Output = ()> + MaybeSendFuture { ... }
    fn on_progress(
        &self,
        notification: ProgressNotificationParam,
        context: NotificationContext<RoleServer>,
    ) -> impl Future<Output = ()> + MaybeSendFuture { ... }
    fn on_initialized(
        &self,
        context: NotificationContext<RoleServer>,
    ) -> impl Future<Output = ()> + MaybeSendFuture { ... }
    fn on_roots_list_changed(
        &self,
        context: NotificationContext<RoleServer>,
    ) -> impl Future<Output = ()> + MaybeSendFuture { ... }
    fn on_custom_notification(
        &self,
        notification: CustomNotification,
        context: NotificationContext<RoleServer>,
    ) -> impl Future<Output = ()> + MaybeSendFuture { ... }
    fn get_info(&self) -> InitializeResult { ... }
    fn get_task(
        &self,
        request: GetTaskParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<GetTaskResult, ErrorData>> + MaybeSendFuture { ... }
    fn update_task(
        &self,
        request: UpdateTaskParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture { ... }
    fn cancel_task(
        &self,
        request: CancelTaskParams,
        context: RequestContext<RoleServer>,
    ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture { ... }
}

Available on crate feature mcp and crate feature server and crate feature tools and non-crate feature local only.

Provided Methods

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

fn initialize( &self, request: InitializeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<InitializeResult, ErrorData>> + MaybeSendFuture

fn supported_protocol_versions(&self) -> Cow<'static, [ProtocolVersion]>

Return the protocol versions supported by this server.

Defaults to every version this SDK knows. Override it to narrow the set to the revisions the server actually implements: the returned list is advertised by Self::discover, bounds what initialize negotiation may agree to, and is what per-request versions are validated against.

fn discover( &self, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<DiscoverResult, ErrorData>> + MaybeSendFuture

Return this server’s discovery information.

fn complete( &self, request: CompleteRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<CompleteResult, ErrorData>> + MaybeSendFuture

fn set_level( &self, request: SetLevelRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

fn get_prompt( &self, request: GetPromptRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<GetPromptResponse, ErrorData>> + MaybeSendFuture

fn list_prompts( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListPromptsResult, ErrorData>> + MaybeSendFuture

fn list_resources( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListResourcesResult, ErrorData>> + MaybeSendFuture

fn list_resource_templates( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListResourceTemplatesResult, ErrorData>> + MaybeSendFuture

fn read_resource( &self, request: ReadResourceRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ReadResourceResponse, ErrorData>> + MaybeSendFuture

fn accepted_subscription_filter( &self, requested: &SubscriptionFilter, ) -> Option<SubscriptionFilter>

Return the subset of a requested notification filter this server accepts.

Returning None leaves subscriptions/listen unimplemented. The SDK intersects the returned filter with both requested and the notification capabilities advertised by Self::get_info before acknowledging it. Categories that were not requested or advertised are always removed.

fn listen( &self, context: SubscriptionContext, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

Run one established subscription until it is cancelled or closed gracefully.

The SDK sends the acknowledgment before invoking this method. Returning Ok(()) sends the final SubscriptionsListenResult defined by the 2026-07-28 schema, marking graceful server teardown. Explicit stdio cancellation uses notifications/cancelled instead.

fn subscribe( &self, request: SubscribeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

👎Deprecated:

resources/subscribe is legacy-only; implement accepted_subscription_filter and listen for protocol version 2026-07-28

fn unsubscribe( &self, request: UnsubscribeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

👎Deprecated:

resources/unsubscribe is legacy-only; subscriptions/listen is cancelled through its request lifecycle

fn call_tool( &self, request: CallToolRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<CallToolResponse, ErrorData>> + MaybeSendFuture

Handle a tools/call request from a client.

Choosing a return value

MCP distinguishes two failure modes; the API forces you to pick the right one explicitly because they reach the caller’s UI very differently:

• Ok(CallToolResult::error(...)) — the tool ran (or tried to) and produced a failure the caller should see. The content you supply is rendered in the caller’s MCP client, so the user gets your message. This is the right return value for almost every “the tool didn’t work” path — empty results, validation failures the user can fix, downstream service unavailability, etc.

• Err(McpError) — a JSON-RPC protocol error. Use this only when the request itself is unroutable: unknown tool (ErrorCode::METHOD_NOT_FOUND), malformed request shape that cannot be treated as a valid tools/call, or a server-internal failure that means the server cannot serve any request right now (ErrorCode::INTERNAL_ERROR, -32603). MCP clients typically render protocol errors opaquely; the caller will not see your message — they see something like “Tool result missing due to internal error”. If you want the caller to read your error, use Ok(CallToolResult::error(...)).

See CallToolResult::error for a worked example.

fn list_tools( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListToolsResult, ErrorData>> + MaybeSendFuture

fn get_tool(&self, _name: &str) -> Option<Tool>

Get a tool definition by name.

The default implementation returns None, which bypasses validation. When using #[tool_handler], this method is automatically implemented.

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

fn on_cancelled( &self, notification: CancelledNotificationParam, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_progress( &self, notification: ProgressNotificationParam, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_initialized( &self, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_roots_list_changed( &self, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

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

fn get_info(&self) -> InitializeResult

fn get_task( &self, request: GetTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<GetTaskResult, ErrorData>> + MaybeSendFuture

SEP-2663 tasks/get: return the current DetailedTask state.

fn update_task( &self, request: UpdateTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

SEP-2663 tasks/update: accept responses to outstanding in-task input requests. Returns an empty acknowledgement on success.

fn cancel_task( &self, request: CancelTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

SEP-2663 tasks/cancel: cooperative cancellation. Returns an empty acknowledgement; the task’s observable status may lag.

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementations on Foreign Types

impl<T> ServerHandler for Box<T>

where T: ServerHandler,

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

fn initialize( &self, request: InitializeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<InitializeResult, ErrorData>> + MaybeSendFuture

fn supported_protocol_versions(&self) -> Cow<'static, [ProtocolVersion]>

fn discover( &self, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<DiscoverResult, ErrorData>> + MaybeSendFuture

fn complete( &self, request: CompleteRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<CompleteResult, ErrorData>> + MaybeSendFuture

fn set_level( &self, request: SetLevelRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

fn get_prompt( &self, request: GetPromptRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<GetPromptResponse, ErrorData>> + MaybeSendFuture

fn list_prompts( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListPromptsResult, ErrorData>> + MaybeSendFuture

fn list_resources( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListResourcesResult, ErrorData>> + MaybeSendFuture

fn list_resource_templates( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListResourceTemplatesResult, ErrorData>> + MaybeSendFuture

fn read_resource( &self, request: ReadResourceRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ReadResourceResponse, ErrorData>> + MaybeSendFuture

fn accepted_subscription_filter( &self, requested: &SubscriptionFilter, ) -> Option<SubscriptionFilter>

fn listen( &self, context: SubscriptionContext, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

fn subscribe( &self, request: SubscribeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

👎Deprecated:

resources/subscribe is legacy-only; implement accepted_subscription_filter and listen for protocol version 2026-07-28

fn unsubscribe( &self, request: UnsubscribeRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

👎Deprecated:

resources/unsubscribe is legacy-only; subscriptions/listen is cancelled through its request lifecycle

fn call_tool( &self, request: CallToolRequestParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<CallToolResponse, ErrorData>> + MaybeSendFuture

fn list_tools( &self, request: Option<PaginatedRequestParams>, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<ListToolsResult, ErrorData>> + MaybeSendFuture

fn get_tool(&self, name: &str) -> Option<Tool>

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

fn on_cancelled( &self, notification: CancelledNotificationParam, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_progress( &self, notification: ProgressNotificationParam, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_initialized( &self, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

fn on_roots_list_changed( &self, context: NotificationContext<RoleServer>, ) -> impl Future<Output = ()> + MaybeSendFuture

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

fn get_info(&self) -> InitializeResult

fn get_task( &self, request: GetTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<GetTaskResult, ErrorData>> + MaybeSendFuture

fn update_task( &self, request: UpdateTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

fn cancel_task( &self, request: CancelTaskParams, context: RequestContext<RoleServer>, ) -> impl Future<Output = Result<(), ErrorData>> + MaybeSendFuture

Implementors

impl<T> ServerHandler for Arc<T>

where T: ServerHandler,