One API is a client library that enables you to connect and trade on multiple FICC trading venues. We translate the trading venue APIs into the format used by TransFICC, to allow for easy/single integration – so connecting to a new venue is just a simple configuration change.
We also manage changes to APIs, when trading venues change fields or perform an upgrade. It's a hosted service so hardware and venue connectivity issues are all managed by us.
We use a client library as it provides better documentation and pre-built sample code, making connectivity easier and faster for our clients.
This 40 second animation provides an overview of One API, including how it manages complex trading workflows.
Don't just take our word for it, look at this feedback from one of our clients...