I'd like this service a lot more if it had a "last_refreshed" field. BGP/network-announcement hijacks aren't exactly common, but it'd be a useful bit of info to have in terms of determining how reliable the announcement is.
By "reliable" it sounds like you mean "legitimate"? As in, $asn is "authorized" to announce $prefix? "originAS" exists for that purpose.
Also, it's not clear what they're (ipinfo.io) using as their source for the ASN. Are they simply reporting the ASN as provided by ARIN, etc., or are they actually running BGP and reporting the origin ASN as they see it in announcements. My money would be on the former, in which case any prefix hijacking would not affect the data reported by ipinfo.io.
I don't think a "last_refreshed" date would be that helpful, though. Netblocks aren't being shuffled around very often. I just looked at a previous employer's assignments and it was almost a decade ago that it was last updated. It's still 100% accurate, however.
Regardless, if you want it, that data is available from the RIRs. Go crazy.
