You have to specify from what part of query your object should be constructed. Url.Action pass parameters to uri, so probably you need that ([FromUri] added):

public IActionResult GetDocuments([FromUri]AreaVM area)

Read this for more details: https://learn.microsoft.com/en-us/aspnet/web-api/overview/formats-and-model-binding/parameter-binding-in-aspnet-web-api#using-fromuri