Improve helpers performance

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

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

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

No file, test, or entry point is named. Start by locating the handlers and helper code responsible for the reported errors, then review how those errors are currently surfaced. Done means the relevant error messages are more descriptive and the behavior is covered by appropriate tests.

索引モデルが issue の本文から書いたものです。