MediaWiki:Apihelp-query+messagecollection-param-prop/en

Which properties to get:
 * definition:Message definition.
 * translation:Current translation (without $1 string if any, use the tags to check for outdated or broken translations).
 * tags:Message tags, like optional, ignored and fuzzy.
 * properties:Message properties, like status, revision, last-translator. Can vary between messages.
 * revision: Deprecated! Use $2prop=properties.