Depends on your country and employer. In some situations, your job description could be a big deal. For example if you’re in a union, you are probably required to only do the specific tasks as described in the job description.
Some countries may also have laws about your work contract. If that applies to you, then it’s probably important on your employer’s part to have the right description for your job.
But in many places, it really doesn’t matter: your job description vs what you actually do, as long as you aren’t being asked to do something that needs licensure or other regulations. Many job descriptions will have a catch-all like “… And other duties as directed” to fill in the gap.