Content pillars
The three or four recurring subjects an account posts about, agreed in advance so every post is not a fresh decision.
Without them a calendar becomes a series of individual ideas, each argued from scratch, and the account reads as a stream of unrelated posts. With them the question changes from “what do we post” to “what is the next one of these”, which is a question somebody can answer on a Tuesday.
Three or four is the working range. Two is a monologue. Six is a magazine, and nobody has the resources to run a magazine. The fourth pillar is very often the one that turns out to carry the account.
They should come from what the business actually knows. A pillar you cannot restock every month is a pillar you will quietly abandon in the second quarter.