To use the SmartPM API you will likely need to chain multiple API calls together.
The first API call that you will want to make is a call to get active projects. Once you have received the active projects in your company, you will then want to either get a list of all the scenarios that exist for that project or use the defaultScenarioId (primary scenario) or originalScenarioId(All Schedules -> Full Schedule) and get the scenario details for each scenario.