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, not from what performs on somebody else’s account. A pillar you cannot restock every month is a pillar you will quietly abandon in the second quarter.