FineRx MCP demonstrates solid definition quality with consistent naming patterns (verb-first: compare_, find_, get_, search_, email_), comprehensive parameter descriptions, and explicit JSON Schema definitions. All 14 tools have descriptions and typed input schemas. However, output schemas are not documented in the visible code, parameter constraints lack formal enums (e.g., locale accepts free-form strings instead of an enum of 12 supported languages), and error handling guidance is absent. Tool descriptions are domain-specific but could be more concise for LLM parsing (some exceed 200 chars). The server correctly implements tool annotations (readOnlyHint, destructiveHint) for 13 read-only and 1 write tool, supporting proper agent planning.

• Document output schemas for all tools. Include field names, types, and descriptions. Example: 'Returns {prices: [{chain: string, amount: number, date: ISO8601, ...}], total_count: number, next_cursor?: string}'.
• Convert locale parameters to enum constraints: {"type": "string", "enum": ["en", "es", "zh", "vi", "tl", "ar", "ko", "ru", "pt", "ht", "fr", "tr"]}. This prevents invalid input and self-documents the tool.
• Add error handling guidance to tool descriptions. Example: 'If the drug is not found, returns error code DRUG_NOT_FOUND with available alternatives. Try search_drugs() with a partial name.'
• Shorten tool descriptions to 100 - 150 characters for better LLM parsing. Current descriptions (e.g., compare_prices at ~180 chars) are readable but verbose. Focus on WHAT and WHEN, not implementation details.
• Add format constraints to string parameters: zip should specify '5-digit US ZIP code (e.g., 10001) or city name (e.g., New York, NY)'; drug should clarify 'Drug name (e.g., lisinopril) or slug (e.g., lisinopril-10mg)'.