I've been looking into starting to use the API for some of the userscript features and was wondering:

Is there any way to request info on multiple post id's at once?

The id parameter works fine when requesting just one but I figured I'd ask if there's any method available so I don't have to send an excessive number of requests

You could maybe use "tags=id:>### id:<###" to get a range of ids, but you'll get some unused data.

"tags=( id:### ~ id:### )" is the most ideal way if it works, but the ~ operator doesn't seem to work on metatags.

Yeah unfortunately that doesn't seem to work. Searching for just one id does but that's functionally the same as submitting the id directly.