The tool namespace needs to be explicitely declared inside your manifest header.
Add this attribute to your manifest markup :
xmlns:tools=”http://schemas.android.com/tools”
As a result your header will look like :
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
package="com.Guru.Hwelth">
cf.
[Tools: replace not replacing in Android manifest