How to add @ mention in response to slash commands in slack

Question

How can I make slack parse @someone mentions as links to the user instead of plaintext. I've been reading slack documentation on message formatting but still haven't figured it out. Here's an example of what I'm getting now:

{
  "text": "*username:* @alexis",
  "response_type": "ephemeral"
}

Answer 1

To make a proper "clickable" mention, you need to pass the unique user ID and not the plaintext name.

The format of the user ID is: U024BE7LHand a mention would look like this: <@U024BE7LH>

Ther user ID of the user that executed the slash command will be in the payload that slack sends to your endpoint. You can also look up user IDs by calling the users.list method, which will give you access to the user IDs of all the users in the team.

More information here