API for a web service, couple new features and browser extensions

I have a website that takes a text field input and breaks long messages into multiple shorter 140 character messages that can be sent to Twitter in one click (it connects to a user's account via Oauth). This is done client-side as you type using Javascript. I want to: 1) Add a couple of features on how to handle long messages (Tweet text as image, Tweet extract in one single message with link for full text) 2) Create an API for third party applications to use the service. This API should allow authenticating the third-party making an API call, keep track of how many API calls are made by each application and using which tweet method (split, link, image), optionally set a limit to the number of API calls. 3) Create browser extensions that add a button on [login to view URL] (next to Tweet button) whenever text is longer than 140 characters (example attached). This browser extension will use the API to interact with the service just as other third party apps would. ** VERY IMPORTANT ** - Project will be awarded only after discussing all specifics with bidders to make sure everything is clear and you are 100% sure to have the skills required, so ask away whatever comes to mind. - I prefer hiring someone with the profile to handle all three tasks described above. However, if you are an a expert on APIs but not browser extensions and would like to take on the project, I'm open to doing just part of the project if the price is right. I need someone that can deliver reliable, clean code. The time it takes to complete is important but secondary to quality.