You can use the following API to get a tag value:

public Object getTagValue(Object_ object, String tagName) throws Exception {
...
}

If the RuntimeObject is omitted, $context$ or self will be used as an object. The context object in the parametric is the constraint block object that owns the constraint, not the actual context of the diagram. The following example shows how to get a tag value without specifying a RuntimeObject in ALH API:

public Object getTagValue(String tagName) throws Exception {
...
}