making post request with createAsyncThunk redux toolkit

Question

Following is my reduxtoolkit code. I am trying to post data but it is giving me 422 error. The response says spot_id and item_id required but I am sending it. Am i doing anthing wrong?

export const postData = createAsyncThunk(
  'items/addItem',
  async (data, thunk) => {
    const accessToken = await getStorageValue("accessToken")
    const axios = await axiosMaker()

    const newItem = new FormData()
    newItem.append("spot_id", data.spotId)
    newItem.append("item_id", JSON.stringify(data.itemId))
    try {
        const response = await axios.post('add_item',newItem , {
            headers: {
                authorization: `Bearer ${accessToken}`,
            },
        })
        console.log("it is success",response.data)
        return response.data
    } catch (error) {
        console.log("it is failure",error)
        return thunk.rejectWithValue("error")
    }
}

)