Why keyof Record wont actually give the keys of the record ?

type GlobalStuff = {
  description : C,
  validate : (descriptionKeys : Record<keyof C, string> | undefined) => Boolean
}

type C = Record<string,object>


const test : GlobalStuff = {
  description : {
    test: {}
  },
  validate : (descriptionKeys) => {
    //no auto completed
    descriptionKeys.test
    return true
  }
}