Vendor Issues with Agent Handling

I’ve got a vendor who is providing a VoIP enterprise contact center solution for my client (who need to be namless)
I’ve got over 30 years in telecom and contact center, but these guys are having trouble understanding the concept that in an enterrpise environment, you need 2 things to handle a call: Pipe and Agents
What has happened is the system designed for my client is reserving agent resources without the necessary bandwidth to handle a call (aforementioned pipe) and then when the pipe is not available, forcing that agent into a “not ready” state and proceeding down the list to the next available agent.
This continues until all available agents have been forced into “not ready”.
I know how it’s supposed to work, but does anyone know where I can find some basic best practice documents that state the obvious….
NEVER take and agent out of the queue to handle a call unless you have the pipe to get them that call!
Thanks,
Jeff