Web API中基于令牌的身份验证，无需任何用户界面

I am developing a REST API in ASP.Net Web API. My API will be only accessible via non-browser based clients. I need to implement security for my API so I decided to go with Token based authentication. I have a fair understanding of token based authentication and have read a few tutorials, but they all have some user interface for login. I don't need any UI for login as the login details will be passed by the client through HTTP POST which will be authorized from our database. How can I implement token based authentication in my API? Please note- my API will be accessed in high frequency so I also have to take care of performance. Please let me know if I can explain it any better.I am developing a REST API in ASP.Net Web API.