I've reached out to Tastyworks about their API to connect to MC, and this is their response: Thank you for reaching out - I am happy to help. We are currently working on APIs to be used with third-party software, there is no concrete release date on these quite yet, we are hoping it will be before ...

Since the NT / Tradovate merger, Tradovate's credentials can be used to trade on NT (web or desktop). Tradovate already has an API. Can this API be accessed within MultiCharts?

MultiCharts said Tradovate may be traded via Rithmic. Anybody managed to place on Tradovate via MC?

IG Markets is also available in the US markets, after they acquired TastyTrade. Hopefully IG will be added as a broker to MC soon.