Method - Extract the substring starting from the index of "Alert Id", By using the substring function.

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1. Taken your given out put in the compose action, and being converted to string with function string(outputs('Compose_Output'))

2. Again, compose action using substring to start from the index of "Alert Id" with function - substring(outputs('Convert_to_String'), outputs('Compose'), 147)

3. Created - Set Variable "Alert Id" as required output : Alert Id*: ```/subscriptions/32476574-bf58-4703-96d9-4378327845/providers/Microsoft.AlertsManagement/alerts/629bd98a-f9b5-c79a-75b1-b807b48d0002```

4. Schema::

{
    "definition": {
        "$schema": "https://schema.management.azure.com/providers/Microsoft.Logic/schemas/2016-06-01/workflowdefinition.json#",
        "contentVersion": "1.0.0.0",
        "triggers": {
            "When_a_HTTP_request_is_received": {
                "type": "Request",
                "kind": "Http"
            }
        },
        "actions": {
            "Compose_OutPut": {
                "runAfter": {
                    "Alert_Id": [
                        "Succeeded"
                    ]
                },
                "type": "Compose",
                "inputs": ":azure: :alert: \n*Non-Prod Alert: RuleCpupercetange*\n*Severity*: Sev4\n*Timestamp*: 2024-10-10T17:55:18.5144302Z \n*Alert Id*: ```/subscriptions/32476574-bf58-4703-96d9-4378327845/providers/Microsoft.AlertsManagement/alerts/629bd98a-f9b5-c79a-75b1-b807b48d0002```\nClick here to find the code \n*****************************************************\n*Affected resource: W008ssaltmost* \n*Resource modified by:[email protected]*\n*****************************************************\n*Select a response:*, with interactive elements"
            },
            "Convert_to_String": {
                "runAfter": {
                    "Compose_OutPut": [
                        "Succeeded"
                    ]
                },
                "type": "Compose",
                "inputs": "@string(outputs('Compose_OutPut'))"
            },
            "Alert_Id": {
                "runAfter": {},
                "type": "InitializeVariable",
                "inputs": {
                    "variables": [
                        {
                            "name": "Alert Id",
                            "type": "string"
                        }
                    ]
                }
            },
            "Set_Variable_Alert_Id": {
                "runAfter": {
                    "Compose_to_set_variable": [
                        "Succeeded"
                    ]
                },
                "type": "SetVariable",
                "inputs": {
                    "name": "Alert Id",
                    "value": "@outputs('Compose_to_set_variable')"
                }
            },
            "Compose": {
                "runAfter": {
                    "Convert_to_String": [
                        "Succeeded"
                    ]
                },
                "type": "Compose",
                "inputs": "@indexOf(outputs('Convert_to_String'), 'Alert Id')\r\n"
            },
            "Compose_to_set_variable": {
                "runAfter": {
                    "Compose": [
                        "Succeeded"
                    ]
                },
                "type": "Compose",
                "inputs": "@substring(outputs('Convert_to_String'), outputs('Compose'), 147)\r\n"
            }
        },
        "outputs": {},
        "parameters": {
            "$connections": {
                "type": "Object",
                "defaultValue": {}
            }
        }
    },
    "parameters": {
        "$connections": {
            "type": "Object",
            "value": {}
        }
    }
}