Not-so-obvious tags and Pixiv

Question: Can we only tag based on what the image actually shows us (along with artist names gleamed from their websites)?

There's at least one image that is tagged "futanari" on pixiv, but here, the image itself cuts off right at the pubic hair line, obscuring any male genitalia (though there is a link to a child post which shows the whole image, and that one does show that it is, in fact, a futanari image). The "cut-off" image is sourced, but I've been unable to locate a source for the "full" image. Given this, should the cut-off image also be tagged "futanari", even though it's not obvious from that image alone?

Thanks.

When you search for a tag, do you want images that do not have that tag pictured? Just because there is the "complete" version that has it is no reason to start tagging elements that aren't there.

Purely context-based tags (bespectacled, alternate_hairstyle) are used on danbooru, but there aren't a lot of them, and generally they're not used in this kind of situation.

I would not add the tag.

In the case of context, we sometimes rely on the artist's comments or notes to fill in the gap (for example for a tag like prostitute). But in this case, I don't think it's appropriate. As jxh2154 says, the best way to go about it when in doubt is to think "if I was searching for images with {tag}, would I want to find this image?"

This kind of tagging goes very much against our policy of tagging only things based on visual evidence in the image itself. While there are exceptions, as jxh2154 notes, they are infrequent and usually carefully discussed beforehand. Tagging futanari based on the existence of another picture is stupid and pointless, as tags are supposed to describe *this* picture, not some other picture possibly in existence.

That's all I was looking for. Thanks for the responses.