Single tool with reasonable naming and acceptable description, but significant gaps in parameter documentation, output schema clarity, and error handling guidance. The tool name 'read_document' follows verb_noun convention correctly. Description is present but lacks context about error scenarios and return format. Input schema exists but lacks depth in constraint documentation. No output schema is documented for the LLM. Error handling returns plain strings rather than structured guidance.

• Document the output schema explicitly. Example: 'Returns a string containing extracted text. On error, returns a string starting with 'Error: ' describing the problem and suggesting recovery (e.g., 'Error: File not found. Check the path and try again' or 'Error: Unsupported format. Supported types: .txt, .docx, .pdf, .xlsx, .xls').'
• Restructure error responses to guide recovery. Instead of catching all exceptions and returning strings, categorize them: FileNotFoundError → 'user-fixable' with suggestion 'verify the file path'; UnsupportedFormatError → 'user-fixable' with suggestion 'check file extension'; generic exceptions → 'retryable' with suggestion 'try again'.
• Add explicit constraint to the 'filename' parameter: 'A valid file path (absolute or relative) to a document file. Supported formats: .txt (UTF-8, GBK, GB2312, Latin-1), .docx, .pdf, .xlsx, .xls. The path will be resolved relative to the current working directory if relative.'
• Document maximum file size or performance characteristics. Example: 'Large files (>100MB) may be slow or truncated. PDFs with scanned images (no OCR) may return minimal text.'
• Consider adding a 'dry_run' or validation mode. Tools that process files should ideally support a check that validates the file without fully extracting text, reducing waste for very large files.
• Return structured error objects instead of plain strings. Current implementation returns 'Error: ...' as a string. A structured format like {status: 'success'|'error', data: '...', error: {code: 'FILE_NOT_FOUND'|'UNSUPPORTED_FORMAT'|..., message: '...', suggestion: '...'}} would enable better LLM error handling.