As much as you can assess and are willing to pay for. Those two limits are stricter than they sound, and together they set the size of a pitch request.
The first limit: what you can assess
Ask for a finished campaign with three channels and a media plan and you will get three fifty-page documents. Nobody on your steering group reads all three in full, and then the presentation decides. You had a lot of work produced in order to choose worse.
Ask for a strategic direction with one worked-out example and everyone can read it, compare it and talk about it. That is better for your decision and cheaper for everyone.
The second limit: what you pay for
Everything you ask beyond a meeting is work that cannot be billed to another client. Whoever asks a lot and pays nothing gets, in practice, the work of whoever had time to spare, and those are rarely the strongest teams. See should I pay a pitch fee.
What to ask for
- How they read the problem. Their reframing of your briefing says more about their thinking than any design.
- A direction, with one execution showing what that direction means in practice.
- The team, with names and availability.
- The approach and the planning, because that is how they will work later too.
- The price in units of work, so you can see where their hours go.
What not to ask for
- Full production. A finished film or a built website in a pitch is waste: you are buying a team for years, not a two-week delivery.
- Several complete concepts per agency. That dilutes their best thinking across three ideas, two of which exist to be dropped.
- Detailed media work before the strategy is settled. That is arithmetic on an assumption.
The rule of thumb
What you see in a pitch is a promise about how someone thinks. You are not buying a campaign, you are buying a team. Size your request accordingly and you will get better answers from better agencies.
Whether your request is proportionate to what you can say about it shows up fastest in your own briefing. IKAg's briefing analysis walks through it.
See also: how to write a briefing and may I use the work from a pitch.