/posts/{ids} reports that it requires an access token, but that's not documented

Question

Hitting the following URL:

https://api.stackexchange.com/2.2/posts/25860304?key=<valid key>&filter=!b0OfN.wXSdUuN(&pagesize=100&site=stackoverflow

I'm getting a HTTP 400 (Bad Request) response with the following content:

{
    "error_id": 401,
    "error_message": "This method requires an access_token",
    "error_name": "access_token_required"
}

However, the /posts/{ids} endpoint isn't documented as requiring an access token, and the API console doesn't provide an input for one.

What gives?

Answer 1

Your filter includes all fields, including info on whether the current user upvoted the post. This information requires an access token to determine the user.

The docs page for the post type states that upvoted and downvoted are private_info.