How to pass grouping by login page in API request?

Question

API

You need to take statistics through the API on the login page (more grouping ym:s:searchEngine). In the documentation, it is listed as dimensions (grouping). But request with
dimensions = "ym:s:startURLPath=='/igrushki/'"
(only encoded) doesn't work and returns error invalid_parameter.
If you substitute the same attribute in the filters, then the data is returned, but the results do not correspond to the report in the metric.
How to make the login page work?

Answer 1

The problem was solved, and consisted in the fact that within the framework of filtering it was necessary to use the "contains a substring" operator ([email protected]), instead of strict filtering with the "==" operator.
That is, in the end it should look like this:
filters = "ym:s:[email protected]'/igrushki/'"Of course, encoded.