From what I know about Microsoft Planner, you don’t have any API trigger that you could set to directly to n8n. The best way would be to use the Microsoft Automation tool called Power Automate, link it to your planner and setup rules for your tasks. From there, you should be able to setup triggers and add HTTP actions to link PA to n8n. It shall require a bit of configurations I guess but this appear for me the only way.