What should a marketing retainer actually cover?
A retainer is a standing invoice for work nobody itemises, which is fine when the work is real and invisible when it is not.
What should be in a retainer?
A defined list of what happens every month, a named deliverable, and a report showing what changed. If none of those exist, you are buying availability rather than work.
What do we include, and why?
Hosting and security, prompt re-tuning after model updates, weekly review of real conversations, integration maintenance, the monthly report, and running whichever departments are attached.
The model-update item is the one people have not usually considered. A foundation model changing can alter how an agent reads its instructions, so an agent nobody re-tests is one drifting quietly.
How do I know a retainer is still earning its keep?
Ask what the last three months' reports said and whether anything changed as a result. A report nobody acts on is a subscription, and cancelling it usually changes nothing, which is the answer.