Capabilities
The platforms, protocols and tooling in regular use. If something you run is not on this list, it is worth asking — adjacent systems are usually a short bridge.
Control platforms
Protocols & interfaces
Networking
AV & performance systems
Software & infrastructure
Working practice
Vendor-neutral by default.
Equipment gets specified against the requirement, the service situation and what the client's own people can maintain — not against whatever carries the best margin that quarter.
Where a specific product genuinely is the right answer, the reasoning goes in the documentation so the next person understands the choice.