I manage to fetch movies from my private list, or the top_rated endpoint, but struggle with authentication issues when trying to add or delete movies from my list.

Here is my code:

payload = {
    "media_id": movie_id_to_delete
}

url = f"https://api.themoviedb.org/3/list/{my_top_1000_list_id}/remove_item?api_key={tmdb_api_key}"

headers = {
    "Content-Type": "application/json; charset=utf-8"
    }

res = requests.post(url, headers=headers, json=payload)

print(f"{res.status_code=}")
print(f"{res.json()=}")

outputs:

res.status_code=401
res.json()={'success': False, 'status_code': 3, 'status_message': 'Authentication failed: You do not have permissions to access the service.'}

What am I doing wrong?