Maybe something like json-ld schema? https://schema.org/Person
I wouldn't but age in there. Not for PII reasons but I doubt I would remember to update it every year... My own website I changed to just say what decade my age is to give me some leeway.
Good idea though will change mine now.
The profile is used by other things as well such as keybase verification etc.
perhaps birth year?
There is! It's called microformats[1] and is a very minimal format to embed machine readable data inside of html via standardized class names. The format for a person would be an h-card[2]. There are a bunch of parsing libraries for multiple programming laguages, such as https://go.microformats.io/.
For example if you enter my website url in there you get all the data as a nice json object: https://go.microformats.io/?url=https%3A%2F%2Ftiim.ch
[1]: http://microformats.org/ [2]: http://microformats.org/wiki/h-card
Something like: