where $params is an associative array with the same keys as you can use for the content/tree fetch function ( http://ez.no/doc/ez_publish/technical_manual/3_8/reference/modules/content/fetch_functions/tree ) in the templates. Then you can use the attribute_filter key to filter on attributes.
you're right, i want to fetch data from the CLI script ... your help was useful ! it works ... (thanks a lot for your article "about Fetching eZ publish content objects with PHP", it's nice to understand kernel ... :-) )