When an outsourced process disappoints, the post-mortem usually finds the same thing: the provider did what was written down, and what was written down was not what the business actually did. The knowledge lived in two or three people's heads, and it never made the journey.
You do not need a full operations manual before you start. You need six things.
1. The trigger and the finish line
What starts a unit of work (an email, a ticket, a nightly file) and what state means it is done. Ambiguity at either end multiplies through everything between.
2. The exceptions you handle every week
Ask the person who does the job which cases annoy them. Those are the exceptions. Write down what they do about each one. Ten exceptions, honestly described, are worth more than a hundred pages of the happy path.
3. The decisions that are yours
Which decisions must stay with you, such as approving a large discount, writing off a balance or promising a customer a refund. State them explicitly so the provider escalates rather than guesses.
4. What good looks like, with examples
Three examples of work you were happy with and three you were not, with a sentence on why. This calibrates quality faster than any rubric.
5. The systems and who can see what
Every tool the process touches, what access it needs, and what data must not leave your environment. This drives the security setup and avoids a delayed start.
6. The calendar
Deadlines, cut-offs, peak periods and the dates that cannot slip. The provider should build their staffing around these; they can only do so if they know.
Do this well and a good provider will turn it into a proper procedure library within the first weeks. Skip it and you will spend the same time later, under pressure, and after the first mistake.