Custom API module

We need a small custom drupal 7 module. We have the API description, but it is in german language. This is what needs to be done: Username und API key are saved in user account. Basic URL looks like [login to view URL] 4 functions needs to be implemented. add-kw - add's a tracking for a keyword list-kw - list of all added keyword trackings get-ranking - gets ranking for a keyword (only latest, all or beetween a timeframe) credits - gets the actual amount of credits The API answer is in JSON format. A content type or an entity is not available at the moment, it must be created. A view and graphs must noch be created. We can do it ourself. We have an agreement with the API provider. The first 100 Keywords for every user are free. A limit need to be implemented. More then 100 tracking should only be possible when the user has saved his own username an his own api-key in his user profile. Also his used credits an the actual Amount of credits should be showed somewhere. For the first 100 trackings our global username and api-key must be used for the api calls. For the possible errors - "Not enough credits available" at the api provider - the limit of 100 Trackings is reached we need a drupal error messages. Hope I have not forgotten something. We need this module at the end of the week. I can send API description PDF via private message if you want to have a look at it.