@大森 直人 ,
You could refer to chatMessage resource type to learn more about Teams chat API. As we are mainly responsible for general issue of Microsoft Teams, your question involved in development is out of our scope. I would add office-teams-app-dev tag for more technical support.
Besides, you could generate a deep link to a chat as below:
https://teams.microsoft.com/l/chat/0/0?**users**=joe[@](/users/na/?userId=a28c79c1-c609-48db-b55f-1783d1187afb).com,bob[@](/users/na/?userId=a28c79c1-c609-48db-b55f-1783d1187afb).com&**topicName**=Prep%20For%20Meeting%20Tomorrow&**message**=Hi%20folks%2C%20kicking%20off%20a%20chat%20about%20our%20meeting%20tomorrow
For more details, please refer to this article.
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