Can we add some custom field with static value to mongodb find query?

I am trying to add/append API request UId to all the queries that we are making to mongodb, so that we can map requests with slow queries from mongodb logs.

I am doing it in aggregate queries by using '$literal' in projected fields.
My Aggregate queries looks something like :

db.test.aggregate({
        $project: {
            "custom_id": { $literal: "uid" } 
            ..
        }
        ..
    })

Also I can't include each field individually in projected fields and add the "custom_id" field with the static value.