how to make callto: works in adaptive card - microsoft-teams

Question

I am trying to initiate a call when pressing a button within an adaptive card (in microsoft teams)
I add URL as callto:[useremail]
eventhough when I write this in the search bar in chrome it works, but when pressing the button in the adaptive card it gives me an error on the chrome page.
any idea why might this happen?
Edit:
Here's a sample card of what I used:
{
"$schema": "http://adaptivecards.io/schemas/adaptive-card.json",
"type": "AdaptiveCard",
"version": "1.0",
"body": [
{
"type": "Container",
"items": [
{
"type": "ColumnSet",
"columns": [
{
"type": "Column",
"width": "auto",
"items": [
{
"size": "small",
"style": "person",
"type": "Image",
"url": "https://pbs.twimg.com/profile_images/3647943215/d7f12830b3c17a5a9e4afcc370e3a37e_400x400.jpeg",
"selectAction":{
"type": "Action.OpenUrl",
"url": "callto:rex#gmail.com"
}
}
]
}
]
}
]
}
]
}

Answer 1

It looks like links inside Teams don't support any protocols other than the usual HTTP/S. You can turn your callto link into an https link using a redirect URL service like these: https://www.cnet.com/news/10-links-to-shorten-your-links/
If you need to generate your callto links dynamically, I'm not sure how many of those services have API's your bot can use. TinyURL does though.
It's also pretty simple to just host your own redirection service in your own domain. You could even use the same domain that your bot is running on, so your link might end up looking something like this: https://rexbot.azurewebsites.net/api/callto/rex#gmail.com
Also, you might consider getting support for this from Teams directly. You can request that they support more URL protocols.