How to get existing template variables in custom module

So assuming I have some code like this in my template

{exp:channel:entries channel="mychannel"}
<h2>{entry_id}: {title}</h2>
{exp:my_custom_tag:function}
{/exp:channel:entries}

Is it possible to get variables from the parent entries tag (such as entry_id), without explicitly passing them into my_custom_tag? (I already know about $this->ee->TMPL->fetch_param(), but that doesn’t seem to be able to fetch inherited parameters, such as in this case, the entry_id)

Thanks!