vk api type providers way

vk-api.fs

type getter = string->seq<string * string> -> Async<string>
type ResponseWallGet = JsonProvider<"./wall.get.json">

type Api(acess_token : string) = class
    let create (acess_token:string) : getter = 
        fun method_name parameters ->
                async { 
                    let url = sprintf "https://api.vkontakte.ru/method/%s" method_name
                    let query = seq {
                        yield ("acess_token", acess_token)
                        yield! parameters
                    }
                    let! html = Http.AsyncRequest(  url, 
                                                    query=query, 
                                                    meth="GET",
                                                    headers = [ "accept", "application/json" ])
                    return html
                }

    let api = create acess_token
    let unix_time seonds = (new DateTime(1970, 1, 1)).AddSeconds((float)seonds)    
    member x.WallGet(owner_id:int, count:int) = async {
            let! json = api "wall.get" ["owner_id", owner_id.ToString(); "count" , count.ToString()]
            return ResponseWallGet.Parse(json).Response
        }

    member x.WallGetAsync(owner_id:int, count:int) = Async.StartAsTask(x.WallGet(owner_id, count))