To create a filter based on the event parameters (“client”, “whatever”, and “blabla”) you can use the concept of “AND” filtering, as you’ve thought. You create filters for each parameter using the Filter class with a StringFilter or whichever filter type suits your need, then use FilterExpression to combine them with “AND”. In GA4 API, for each parameter you want to add a filter for, it would involve defining a new Filter instance where each Filter.Expression uses a Filter.Types.StringFilter that matches your desired parameter. Finally, assign the filter combination to the RunReportRequest’s DimensionFilter property. In terms of dimensions, when asking “How do I add parameters of the given event to the Dimensions?”, you would add each parameter as a Dimension to your RunReportRequest. Consider the dimension names as “event_param.*paramName*” where *paramName* is “client”, “whatever”, and “blabla” respectively. The addition of parameters as Dimensions should permit the output to include these fields, hence providing an alternate way to filter the data at a later time if so desired.