Great info on using the Microsoft Graph Rest APi to interact with Office365 apps like planner, tasks, ect.
https://docs.microsoft.com/en-us/graph/api/resources/planner-overview?view=graph-rest-1.0
Get to know the api
About the search api
URL examples:
https://blog.lsonline.fr/2019/10/04/microsoft-graph-api-or-sharepoint-rest-api/