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

Message collection filters. Use ! to negate condition. For example !fuzzy means list only all non-fuzzy messages. Filters are applied in the order given.
 * fuzzy:Messages with fuzzy tag.
 * optional:Messages which should be translated only if changes are necessary.
 * ignored:Messages which are never translated.
 * hastranslation:Messages which have a translation regardless if it is fuzzy or not.
 * translated:Messages which have a translation which is not fuzzy.
 * changed:Messages which have been translated or changed since last export.
 * reviewer&#58;N:Messages where the user number N is among reviewers.
 * last-translator&#58;N:Messages where the user number N is the last translator.