[Sashimister]

職務記述書 is the "official" translation of the term "job description". It is used mostly by the Japanese branches of American and European companies. The transliteration ジョブ・ディスクリプション is also commonly used among such companies and other larger Japanese companies. 職務明細書 is the alternative translation.

As OP stated, these terms are used to named the official company document that describes the responsibilities of each post in a company. At least in Japan, it's not common to include the authority of the post. In describing these responsibilities, the desired levels of knowledge and skills required to fulfill the duties are explained in detail.

The word 仕事内容 is bland, broad and too casual-sounding that it's not used for the title of an official document. It's used in shorter help-wanted ads to describe briefly what the job is about. In casual conversation, however, it can be used to refer to the content of the 職務記述書, but not the 職務記述書 itself as a document. 仕事内容 is simply too light a word.