Teams is not displaying my unfurl response - microsoft-teams

Question

I have a Teams integration with link unfurling set up. I have the messaging endpoint pointed to a public ngrok URL and ngrok proxying a local node.js server that returns the example payload Microsoft has in it's documentation.
This is my endpoint (express.js):
app.post('/bot-test', (req, res) => {
res.send({
"composeExtension": {
"type": "result",
"attachmentLayout": "list",
"attachments": [
{
"contentType": "application/vnd.microsoft.teams.card.o365connector",
"content": {
"sections": [
{
"activityTitle": "[85069]: Create a cool app",
"activityImage": "https://placekitten.com/200/200"
},
{
"title": "Details",
"facts": [
{
"name": "Assigned to:",
"value": "[Larry Brown](mailto:larryb#example.com)"
},
{
"name": "State:",
"value": "Active"
}
]
}
]
}
}
]
}
});
});
When I post a URL in a message in Teams, I see it POST to that endpoint and it responds without errors, but nothing shows up in Teams. What's going wrong? I can't find any logs on Microsoft's side either. I would expect that Teams renders a card with the response payload.

Answer 1

Office 365 Connector cards are not supported for link unfurls ("Message extension previews" in MS parlance). Changing the response to a supported card type worked. Unfortunately, MS doesn't surface this problem anywhere and it just silently discards the response. I was able to find a somewhat useful error description by inspecting the network request that went out from the Teams web client, however.
See this for supported card types: https://learn.microsoft.com/en-us/microsoftteams/platform/task-modules-and-cards/cards/cards-reference