I don't have a specific recommendation (I could just give out names of tools that seem to match your needs but I can't really say I've used any), but in your place I'd reconsider your last requirement of "no connection to the DB".

In my view the best docs are the ones that take the least effort to keep up-to-date. Consider a tool that's able to dynamically list and extract schemas from your existing tables and generate a nice HTML or diagram that can be used as a quick and up-to-date reference. That will require little or zero maintenance compared to a manual diagramming tool. So I'd start looking there.

Depending on the project and usage I'd also consider exposing the database through an API. This makes documentation much easier too, as there are tools to auto generate API docs and you'll decouple your DB schema + access from its usage, which has its own benefits.

The ones I found that actually worked and allowed for documenting schema, as well as creating schema and live monitor/update database instances have been commercial.

• Navicat: https://navicat.com
• Jetbrains Datagrip: https://www.jetbrains.com/datagrip/

Here are some open-source ones that might get closer to what you want. You may not find a perfect solution: https://www.holistics.io/blog/open-source-data-modeling-tools/

Generally, I consider using your database schema as an API like this to be a bad architectural choice, especially if you are using an ORM like Django where you don't have direct control over how the schema is structured.

If it was me, I'd prefer to design an interface to allow the other applications access to the data they need, so as to maintain the abstraction between the logical structure of your models and the messy reality of SQL. Build an actual REST API, define an Open API schema to document it.