It would be "helpful" if the external_api implemented a simple "true/false" or "success" return structure that we could just return instead of having to manually construct a simple "result (boolean) type structure.

Something along the lines of, so that we don't all have to simply reproduce the same _returns() function.

new \external_single_structure([

    'result' => new \external_value(PARAM_BOOL, 'True or false')

]);

Or alternatively just allow the web services to wrap any web service method with a success result if it doesn't throw an exception or return a value.