Experimentation helpers

At what point does having someone help with an experiment for flavor (or properties of that person) require that person to contribute towards the bgs beyond just agreeing to saying they were there?
When I did experimentation for the Marinus twins, we specified certain helper-targets, and they did not need to do bgs, but if I was to say, recruit a spiritualist to look at something for me as part of an experiment, is that flavor or too mechanical?
If it’s mechanical, what sort of thing would they be contributing? Arcane/spiritual perception isn’t a bgs skill, and the experimentation points would be coming from me, so I’m unsure how to approach this.

If they have to use a skill of any kind, you need to coordinate/focus to coordinate. Even if it’s not a bgs skill. If they don’t have to use a skill, it’s just flavor.


Thank you! That’s an excellent rule of thumb.