Update models documentation

**Problem**
When working with lib, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

Start by inspecting lib and locating the models documentation and error-handling paths relevant to the request. No specific files or tests are named, so first clarify which documentation sections and error messages should change; done means the requested updates are defined and verified.

Written by the indexing model from the issue text.