Improve error messages in handlers

**Problem**
When working with parsers, 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 locating the parser handlers and reviewing their current error paths and messages. Done means parser failures provide more descriptive, detailed messages that improve debugging and maintenance; the issue does not name specific files or tests to run.

Written by the indexing model from the issue text.