Struct CompositeHandler 

pub struct CompositeHandler { /* private fields */ }

Server composition through handler mounting. A composite handler that mounts multiple handlers with prefixes.

This enables modular server design by combining multiple handlers into a single namespace. Each mounted handler’s tools, resources, and prompts are automatically prefixed to avoid naming conflicts.

Namespacing Rules

• Tools: {prefix}_{tool_name} (e.g., weather_get_forecast)
• Resources: {prefix}://{original_uri} (e.g., weather://api/forecast)
• Prompts: {prefix}_{prompt_name} (e.g., weather_forecast_prompt)

Thread Safety

CompositeHandler is Send + Sync when all mounted handlers are.

Implementations

impl CompositeHandler

pub fn new(name: impl Into<String>, version: impl Into<String>) -> Self

Create a new composite handler with the given name and version.

Example

let server = CompositeHandler::new("my-server", "1.0.0");

pub fn with_description(self, description: impl Into<String>) -> Self

Set the server description.

pub fn mount<H: McpHandler>(self, handler: H, prefix: impl Into<String>) -> Self

Mount a handler with the given prefix.

All tools, resources, and prompts from the handler will be namespaced with the prefix.

Panics

Panics if a handler with the same prefix is already mounted. This prevents silent shadowing of tools/resources/prompts which could lead to confusing runtime behavior.

Example

let server = CompositeHandler::new("main", "1.0.0")
    .mount(weather_handler, "weather")
    .mount(news_handler, "news");

pub fn try_mount<H: McpHandler>( self, handler: H, prefix: impl Into<String>, ) -> Result<Self, String>

Try to mount a handler with the given prefix, returning an error on duplicate.

This is the fallible version of mount for cases where you want to handle duplicate prefixes gracefully rather than panicking.

Errors

Returns an error if a handler with the same prefix is already mounted.

pub fn handler_count(&self) -> usize

Get the number of mounted handlers.

pub fn prefixes(&self) -> Vec<&str>

Get all mounted prefixes.

Trait Implementations

impl Clone for CompositeHandler

fn clone(&self) -> CompositeHandler

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for CompositeHandler

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl McpHandler for CompositeHandler

fn server_info(&self) -> ServerInfo

Returns server information (name, version, description, etc.)

fn list_tools(&self) -> Vec<Tool>

Returns all available tools.

fn list_resources(&self) -> Vec<Resource>

Returns all available resources.

fn list_prompts(&self) -> Vec<Prompt>

Returns all available prompts.

fn call_tool<'a>( &'a self, name: &'a str, args: Value, ctx: &'a RequestContext, ) -> impl Future<Output = McpResult<ToolResult>> + MaybeSend + 'a

Calls a tool by name with the given arguments.

fn read_resource<'a>( &'a self, uri: &'a str, ctx: &'a RequestContext, ) -> impl Future<Output = McpResult<ResourceResult>> + MaybeSend + 'a

Reads a resource by URI.

fn get_prompt<'a>( &'a self, name: &'a str, args: Option<Value>, ctx: &'a RequestContext, ) -> impl Future<Output = McpResult<PromptResult>> + MaybeSend + 'a

Gets a prompt by name with optional arguments.

fn list_tasks<'a>( &'a self, _cursor: Option<&'a str>, _limit: Option<usize>, _ctx: &'a RequestContext, ) -> impl Future<Output = Result<ListTasksResult, McpError>> + MaybeSend + 'a

Lists all active and recent tasks.

fn get_task<'a>( &'a self, _task_id: &'a str, _ctx: &'a RequestContext, ) -> impl Future<Output = Result<Task, McpError>> + MaybeSend + 'a

Gets the current state of a specific task.

fn cancel_task<'a>( &'a self, _task_id: &'a str, _ctx: &'a RequestContext, ) -> impl Future<Output = Result<Task, McpError>> + MaybeSend + 'a

Cancels a running task.

fn get_task_result<'a>( &'a self, _task_id: &'a str, _ctx: &'a RequestContext, ) -> impl Future<Output = Result<Value, McpError>> + MaybeSend + 'a

Gets the result of a completed task.

fn on_initialize( &self, ) -> impl Future<Output = Result<(), McpError>> + MaybeSend

Called when the server is initialized.

fn on_shutdown(&self) -> impl Future<Output = Result<(), McpError>> + MaybeSend

Called when the server is shutting down.