It has reliable sources, and any important or controversial material which is likely to be challenged is cited. The use of citation templates such as {{cite web}} is not required, but the use of <ref></ref> tags is encouraged.
The article reasonably covers the topic, and does not contain obvious omissions or inaccuracies.
It contains a large proportion of the material necessary for an A-Class article, although some sections may need expansion, and some less important topics may be missing. The article should be neutral and devoid of original research. The article should include illustrations if possible, preferably free images.
The article has a defined structure.
Content should be organized into groups of related material, including a lead section and all the sections that can reasonably be included in an article of its kind.
The article is reasonably well-written.
The prose contains no major grammatical errors and flows sensibly, but it certainly need not be "brilliant". The Manual of Style need not be followed rigorously.
The article contains supporting materials where appropriate.
Illustrations are encouraged, though not required. Diagrams and an infobox etc. should be included where they are relevant and useful to the content.
B-class opera articles should contain a full plot synopsis (with embedded notable arias/musical numbers) that is organized within appropriate divisions. The article should thoroughly cover the Background/history of composition, performance history, musical/textual analysis, critical appreciation, and recordings with no obvious gaps, although some aspects of content and style may still need to be addressed. The opera should be placed into context with other works of the same period, and should include an online libretto if at all possible. Preferably, the article should have illustrations, encompassing musical excerpts and audio in addition to relevant images.
