Consider deprecating old services API

**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.

The issue does not name any files, tests, or parser entry points. Start by locating parser error handling and the old services API, then clarify which area is in scope; done should mean the agreed errors are more descriptive and covered by relevant tests.

Written by the indexing model from the issue text.