If a Rule that should apply filters isn’t working as expected, check the Rule’s consequence and filter syntax.
To make a Rule change the search results by applying a filter, use the Add Query Parameter consequence and set the filters search parameter there.
Do not use Return Custom Data for this purpose. That consequence only adds custom JSON data to the search response. It does not apply the value as a search parameter, so it won’t filter the results.
When using the Manual Editor, make sure the filters parameter uses valid JSON and filter syntax. For example, to filter for size 6 and color black:
{
"filters": "size:6 AND color:black"
}