Open Paper Machine is a citation management toolkit with 20 tools spanning DOI conversion, metadata extraction, BibTeX formatting, and PubMed/arXiv search. Code inspection reveals solid parameter schemas with types and descriptions for most tools, but critical gaps in output documentation, error handling guidance, and some naming ambiguity. The server follows a consistent pattern of verb_noun naming (doi_to_bibtex, extract_from_doi) and includes reasonable parameter constraints. However, no tool provides documented return schemas, making it difficult for LLMs to chain outputs or plan downstream calls. Error handling is minimal, most tools return None or stderr output without actionable recovery guidance. Tools like 'identify_type' and 'extract_from_doi' are well-named with clear descriptions, but 'format_entry' and 'fix_common_issues' lack specificity about which issues are fixed and what the output structure looks like. Overall, the server sits at the mid-range (C grade): functional definitions with present schemas and descriptions, but missing the polish and completeness that would make it A-grade.

• Document output schemas for every tool. Example for doi_to_bibtex: 'Returns: BibTeX string (e.g. @article{key, author={...}, title={...}, ...}). Returns None if DOI not found or request fails.'
• Add actionable error messages. Instead of returning None, return structured errors like {error: 'doi_not_found', message: 'DOI 10.1234/invalid not found. Try verify_doi() first to confirm the DOI exists.'}
• Specify the required and optional fields for 'metadata' parameters. Document: 'metadata object with required keys: title, authors (array), year; optional: venue, volume, issue, pages, abstract, doi, pmid'
• Enumerate constraints for all string/numeric parameters. For filepath: 'Absolute or relative path to a .bib file (UTF-8 encoded, must exist)'. For max_results: 'Integer 1 - 100 (default: 50)'. For delay: 'Float 0.1 - 10.0 seconds.'
• Document what fix_common_issues actually fixes. Example: 'Fixes: (1) page ranges from '123 - 456' format, (2) DOI URLs to bare DOIs, (3) author separators from '&' to 'and'. Returns modified entry object.'
• Add per-tool timeout and rate-limit guidance in descriptions. Example: 'May take up to 15 seconds for slow APIs. Implements 0.5 second rate limit between consecutive requests to avoid overwhelming CrossRef.'
• For tools returning arrays (search_google_scholar, search_pubmed), document pagination: 'Returns array of up to max_results items. If more results exist, include next_cursor field for pagination.' Implement cursor-based or offset-based pagination.