API destinations to Microsoft Teams channel

You should use the following architecture: Eventbridge rule -> lambda function -> teams

An AWS EventBridge Rule matches a specific set of AWS events and sends them to a target. The target is a Lambda function that sends the event to a Microsoft Teams Channel using an Incoming HTTP WebHook.

The lambda can execute this example of python code:

import pymsteams
myTeamsMessage = pymsteams.connectorcard("<Microsoft Webhook URL>")
myTeamsMessage.text("this is my text")
myTeamsMessage.send()

This doesn't answer the question directly but have you considered using ChatBot which has teams integration built-in https://aws.amazon.com/blogs/aws/aws-chatbot-now-integrates-with-microsoft-teams/