feat: implement logging/setLevel and silence STDIO

- Add `logging/setLevel` JSON-RPC method
- Define `LogLevel` enum and `SetLevelParams` struct
- Silence startup messages in STDIO transport
- Suppress console logging during STDIO JSON-RPC errors

examples/mcp/inspector/server.vsh

@@ -177,11 +177,9 @@ fn main() {
 		println('  Use JSON-RPC endpoint: http://localhost:${port}/jsonrpc')
 		println('')
 	} else {
-		println('📟 MCP Inspector Server - STDIO Mode')
-		println('====================================')
-		println('Ready for JSON-RPC messages on stdin...')
-		println('')
-		println('💡 Tip: Run with --http --port 9000 for HTTP mode')
+		// In STDIO mode, we should be completely silent to avoid interfering with JSON-RPC communication
+		// The MCP Inspector captures both stdout and stderr, so any output can cause parsing errors
+		// If you need to see startup messages, run with --http mode instead
 	}
 
 	server.start()!

lib/mcp/factory.v

@@ -87,6 +87,14 @@ fn create_tools_call_wrapper(mut server Server) jsonrpc.ProcedureHandler {
 	}
 }
 
+fn create_logging_set_level_wrapper(mut server Server) jsonrpc.ProcedureHandler {
+	return fn [mut server] (request jsonrpc.Request) !jsonrpc.Response {
+		original_json := '{"jsonrpc":"${request.jsonrpc}","method":"${request.method}","params":${request.params},"id":${request.id}}'
+		response_str := server.logging_set_level_handler(original_json)!
+		return jsonrpc.decode_response(response_str)!
+	}
+}
+
 @[params]
 pub struct ServerParams {
 pub:
@@ -122,6 +130,8 @@ pub fn new_server(backend Backend, params ServerParams) !&Server {
 			// Core handlers
 			'initialize':                create_initialize_wrapper(mut server)
 			'notifications/initialized': create_initialized_notification_wrapper()
+			// Logging handlers
+			'logging/setLevel':          create_logging_set_level_wrapper(mut server)
 			// Resource handlers
 			'resources/list':            create_resources_list_wrapper(mut server)
 			'resources/read':            create_resources_read_wrapper(mut server)

lib/mcp/handler_logging.v

@@ -0,0 +1,37 @@
+module mcp
+
+import x.json2
+import freeflowuniverse.herolib.schemas.jsonrpc
+
+// LogLevel represents the logging levels supported by MCP
+pub enum LogLevel {
+	debug
+	info
+	notice
+	warning
+	error
+	critical
+	alert
+	emergency
+}
+
+// SetLevelParams represents the parameters for the logging/setLevel method
+pub struct SetLevelParams {
+pub:
+	level LogLevel
+}
+
+// logging_set_level_handler handles the logging/setLevel request
+// This is a stub implementation that accepts the request but doesn't actually change logging behavior
+fn (mut s Server) logging_set_level_handler(data string) !string {
+	// Decode the request with SetLevelParams
+	request := jsonrpc.decode_request_generic[SetLevelParams](data)!
+
+	// For now, we just acknowledge the request without actually implementing logging level changes
+	// In a full implementation, this would configure the server's logging system
+
+	// Create a success response with empty object (logging/setLevel returns {} on success)
+	empty_map := map[string]string{}
+	response := jsonrpc.new_response_generic[map[string]string](request.id, empty_map)
+	return response.encode()
+}

lib/mcp/server.v

@@ -17,7 +17,7 @@ pub mut:
 
 // start starts the MCP server using the configured transport
 pub fn (mut s Server) start() ! {
-	log.info('Starting MCP server')
+	// Note: Removed log.info() as it interferes with STDIO transport JSON-RPC communication
 	s.transport.start(&s.handler)!
 }
 

lib/mcp/transport/stdio.v

@@ -25,7 +25,8 @@ pub fn (mut t StdioTransport) start(handler &jsonrpc.Handler) ! {
 	unsafe {
 		t.handler = handler
 	}
-	console.print_debug('Starting MCP server with STDIO transport')
+	// Note: In STDIO mode, we should not print any debug messages to stdout
+	// as it interferes with JSON-RPC communication
 
 	for {
 		// Read a message from stdin
@@ -37,23 +38,22 @@ pub fn (mut t StdioTransport) start(handler &jsonrpc.Handler) ! {
 
 		// Parse the JSON-RPC request
 		request := jsonrpc.decode_request(message) or {
-			console.print_stderr('Invalid JSON-RPC request: ${err}')
+			// Note: Removed stderr logging as it can interfere with MCP Inspector
 			// Try to extract the request ID for error response
 			id := jsonrpc.decode_request_id(message) or { 0 }
 			// Create an invalid request error response
 			error_response := jsonrpc.new_error(id, jsonrpc.invalid_request).encode()
-			print(error_response)
+			println(error_response)
 			continue
 		}
 
 		// Handle the message using the JSON-RPC handler
 		response := t.handler.handle(request) or {
-			console.print_stderr('message: ${message}')
-			console.print_stderr('Error handling message: ${err}')
+			// Note: Removed stderr logging as it can interfere with MCP Inspector
 
 			// Create an internal error response
 			error_response := jsonrpc.new_error(request.id, jsonrpc.internal_error).encode()
-			console.print_debug(error_response)
+			println(error_response)
 			continue
 		}