Currently, when a listDatabases command includes a filter, the filter is forwarded to individual shards but is not re-applied to the aggregated result on mongos. This can produce incorrect results in several scenarios:

• sizeOnDisk: A filter on sizeOnDisk is evaluated per shard, but the aggregated sizeOnDisk (summed across shards) may differ from any individual shard's value. A database that correctly passes the filter on each shard individually could fail (or incorrectly pass) the filter when evaluated against the aggregated total.
• shards: The shards property exists only in the aggregated mongos result — it does not exist in individual shard responses. As a result, any filter referencing shards will cause matching entries to be skipped, since the field is absent at the shard level.
• empty: The empty property is calculated differently on mongod vs. mongos.

To fix it, a filter has to be applied to the aggregated result on mongos.

Also, along with the fix, the full coverage tests have to be added for various filter cases and combinations.