Posting a teams channel message with Tag mention is achieved using Graph API via flow with following Url

https://graph.microsoft.com/v1.0/teams/<teamId>/channels/<channelId>/messages

and request body (See Ref. Mention a tag with a flow – Expiscornovus from Dennis )

{
    "body": {
        "content": "Test message <at id=\"0\">SomeTagName</at>. ",
        "contentType": "html"
    },
    "mentions": [
        {
            "id": 0,
            "mentionText": "SomeTagName",
            "mentioned": {
                "tag": {
                    "id": "YABCDEFk5N2EtNjQzZC00MDA3LWEyZTUtNmVjOWM1YWI4NWNiIyM3ODdkMzVhMC0yZWU1LTQ5YzYtYWVkZC1mZDkzYmM0NDlkZDEjI3RrSU1TdGNpMg==",
                    "displayName": "SomeTagName"
                }
            }
        }
    ]
}

Mention block in content <at ...>...</at>, mentionText , and displayName of Tag are easily obtained from Teams UI - name of Tag.

The last piece to build a request body is id of Tag (YABC...kjI3RrSU1TdGNpMg==).

In this post, I will show how to dynamically generate this ID and post message with Tag mention in Power Automate.

How to get Tag IDs via Teams API

As Damien shared in his blog post (Teams Status Update via Power Automate - DamoBird365), undocumented Teams API can be called from Power Automate by leveraging "Send HTTP request to SharePoint" action.

Tag IDs are also retrieved through Teams API with following Url:

GET https://teams.microsoft.com/api/csa/api/v1/teams/<General Channel ID>/tagCards?tagType=any

Response body contains detail information about Tag in given team.

{
  "tagCards": [
    {
      "tagId": "tkIMAtci2",
      "tagName": "Test Tag",
      "memberIds": [
        "8:orgid:b8bc1234-c929-4b08-8228-7109ee7b4545",
        "8:orgid:55551347-6623-4fb3-9694-1d411f03ae5d"
      ],
      "memberCount": 2,
      "tagType": "team",
      "currentMemberIsPartOfTag": true,
      "scheduledMembers": [],
      "version": 1
    }
  ],
  "teamTagSettings": {
    "onlyOwnersCanUpdate": true,
    "tagCount": 1,
    "disallowedSources": [],
    "version": 1
  }
}