Alexa, get skill from LaunchRequest Intent

For every skill there is a unique Skill ID known as applicationId. Making use of this applicationId from the request JSON you can easily determine from which skill the request came in.

You can find this applicationId under application object in every request from Alexa to your backend.

{
    "version": "1.0",
    "session": {
        "new": true,
        "sessionId": "amzn1.echo-api.session.xxxx-xxxx-xxxx-xxxx-xxxxxxx",
        "application": {
            "applicationId": "amzn1.ask.skill.xxxx-xxxx-xxxx-xxxx-xxxx"
        },
        "user": {
            "userId": "amzn1.ask.account.xxxxxxxxxxxxxx"
        }
    },

...

You can also view the Skill ID from Alexa developers console where your Alexa Skills are listed.