Permissions lists and descriptions

I have installed SearchGuard.

Does it exist a documentation that explain the scope of each Elasticsearch permission that is used by SearchGuard?

Or, maybe a class in the Elasticsearch source code?

I have found this documentation ( https://www.elastic.co/guide/en/shield/2.2/privileges-list.html ) but it
only list some permissions… It doesn’t describe each one…

For e.g., I allowed a user to access an index with read/write authorization. I give him the action groups READ/DELETE/WRITE on the index.

However, when he checks if the index exists, a security exception is thrown. I have also to add him the permission “indices:admin/get”.

Now, looking for the existence of the index is OK but I don’t know what additional operations is allowed with that permission…

Thanks.