O que eu estou errando? API GraphQL + Power BI

gistfile1.txt

let
    Source = Json.Document(
        Web.Contents("https://api.prevision.com.br/graphql", 
            [
                Headers=[
                    Method="POST", 
                    Accept="application/json", 
                    UserAuthorization=tokenPrevision
                ], 		
                Content=Text.ToBinary(
                    "query=query SCurve($projectId: int!, $dashboardWeightId: int) {
                        me {
                            project(id: $projectId) {
                                dashboard(id: $dashboardWeightId) {
                                    sCurve {
                                        base {
                                            points {
                                                x             
                                                y
                                            }         
                                        }
                                        expected {
                                            points {
                                                x
                                                y
                                            }
                                        }
                                        realized {
                                            points {
                                                x
                                                y
                                            }
                                        }        
                                    }     
                                }  
                            }  
                        }
                    }",
                    "($projectId:" & pObras_Prevision&")"
                )
            ]
        )
    )
in
    Source