We don't need market data, just order entry. Requirements: 1) Well designed spec that fully defines the protocol (We don't want a situation where we have to confer with someone all the time because "that bit of functionality isn't in the spec, but you have to do x, y and z and it will work") 2) Relatively cheap (maybe < 1/2 cent per share) commissions for around 100k shares/month but the capability to scale as we trade more. Is anyone particularly happy with their current automated broker/api?
Commissions are ok but the API limits your message rate to 50 per sec so you can lag in fast markets, also, it requires TWS to be running in the background last I checked so it isn't quite a 'pure api'.
IB upped messages per sec to 100. I think it is possible to add a second login to a brokerage account, enabling one to distribute requests across multiple TWS instances (please correct me if I'm mistaken). OTOH, you are correct that the IB API is just a socket to the TWS app. I've also encountered stability issues requiring a Ctrl+Alt+Del on TWS.