Does anyone know if the doc _id field has to follow a standard or pattern?

We have a system that uses the path of the URL as doc ID. Everything ran ok until this week when we received a couple of bad requests and transportation errors coming from URLs like this one ../../../example or .. We use the python client and the get function to search the doc by ID, those petitions translated to kibana would be something like this
GET example-index/_doc/../../../example or GET example-index/_doc/.

Thanks in advance for any information or clarification that you could give me.

Hello,

What is the issue you had? It is not clear, it is also not clear how you create your _id as you didn't share any example.

If I'm not wrong the only limitation for the _id field is regarding the size, it needs to be smaller than 512 bytes as described in the documentation.