Need help with relative path and query

I think it is working with below code, you can use it either with the full url or with the relative part and the query.

Maybe the reason why you had trouble is that the API blocks you out when you do too many requests. After waiting a few minutes it will work again.

let
    // Source = Json.Document(Web.Contents("https://mpr.datamart.ams.usda.gov/services/v1.1/reports/2466/Summary?q=report_date=08/05/2019"), 65001),
    pathBase = "https://mpr.datamart.ams.usda.gov/services/v1.1/",
    pathRelative = "reports/2466/Summary?",
    pathQuery = "q=report_date=08/05/2019",
    pathFull = pathBase & pathRelative & pathQuery,
    Source = Json.Document(Web.Contents(pathFull), 65001),
    
    yesterdayDate = DateTime.ToText(Date.AddDays(DateTime.LocalNow(), -1), "yyyy-MM-dd"),
    queryWithTodayDate = "report_date=" & yesterdayDate,
    SourceRelative = Json.Document(
        Web.Contents(pathBase, [
            RelativePath = pathRelative,
            Query = [q = queryWithTodayDate]
        ])
    )
in
    Source