ServerHandler Trait

ServerHandler is the recommended trait for most projects. It provides default implementations for all MCP operations - you override only the methods relevant to your application.

Key Methods

#[async_trait]
pub trait ServerHandler: Send + Sync + 'static {
    async fn on_initialized(&self, runtime: Arc<dyn McpServer>) {}
    // Has a default implementation - only override it to customize initialization.
    async fn handle_initialize_request(
        &self, params: InitializeRequestParams, runtime: Arc<dyn McpServer>
    ) -> Result<InitializeResult, RpcError> { /* default impl */ }
    async fn handle_ping_request(
        &self, _params: Option<RequestParams>, runtime: Arc<dyn McpServer>
    ) -> Result<Result, RpcError>;
    async fn handle_list_tools_request(
        &self, _request: Option<PaginatedRequestParams>, runtime: Arc<dyn McpServer>
    ) -> Result<ListToolsResult, RpcError>;
    async fn handle_call_tool_request(
        &self, params: CallToolRequestParams, runtime: Arc<dyn McpServer>
    ) -> Result<CallToolResult, CallToolError>;
    async fn handle_list_resources_request(
        &self, _request: Option<PaginatedRequestParams>, runtime: Arc<dyn McpServer>
    ) -> Result<ListResourcesResult, RpcError>;
    async fn handle_read_resource_request(
        &self, params: ReadResourceRequestParams, runtime: Arc<dyn McpServer>
    ) -> Result<ReadResourceResult, RpcError>;
    async fn handle_list_prompts_request(
        &self, _request: Option<PaginatedRequestParams>, runtime: Arc<dyn McpServer>
    ) -> Result<ListPromptsResult, RpcError>;
    async fn handle_get_prompt_request(
        &self, params: GetPromptRequestParams, runtime: Arc<dyn McpServer>
    ) -> Result<GetPromptResult, RpcError>;
    async fn handle_complete_request(
        &self, params: CompleteRequestParams, runtime: Arc<dyn McpServer>
    ) -> Result<CompleteResult, RpcError>;
    // ... plus notification handlers, logging, progress, etc.
}

Custom Handler Example

#[async_trait]
impl ServerHandler for MyHandler {
    async fn handle_list_tools_request(
        &self, _request: Option<PaginatedRequestParams>, _runtime: Arc<dyn McpServer>,
    ) -> Result<ListToolsResult, RpcError> {
        Ok(ListToolsResult {
            tools: vec![MyTool::tool()],
            meta: None, next_cursor: None,
        })
    }

    async fn handle_call_tool_request(
        &self, params: CallToolRequestParams, _runtime: Arc<dyn McpServer>,
    ) -> Result<CallToolResult, CallToolError> {
        match params.name.as_str() {
            "my_tool" => Ok(CallToolResult::text_content(vec![TextContent::new(
                "result".into(), None, None,
            )])),
            _ => Err(CallToolError::unknown_tool(params.name)),
        }
    }
}

Convert to a runtime handler with .to_mcp_server_handler().