Looking for pool with API for worker registration

[miner69er2]

I run a large number of machines with significant spare capacity during off-peak hours.
I'd like these machines to register themselves automatically for a pool and do mining during this time.
I haven't found any of the established pools with a scriptable API to register workers -- they all require that you go through some web form to do it.
Is there an established, trustworthy pool with an API for registering new workers?