From OpenStreetMap Wiki
|Describes the main material of a physical feature.|
|Used on these elements|
|Status: De facto|
|Tools for this tag|
Describes the main material of a physical feature.
- material=masonry - if you can, use more specific value instead (e.g. brick)
- more values can be found at Taginfo
Tagging Mistakesmaterial=AG - If you know places with this tag, verify if it could be tagged with another tag. Automated edits are strongly discouraged unless you really know what you are doing!
Rationale: “AG” does not seem to be an established abbreviation in general use for any material.
There are similar material tags in OpenStreetMap. Look at their descriptions if you cannot find the material you want to tag.