The Finnhub MCP server demonstrates solid tool naming and basic structure, but falls short of production-grade quality. All 7 tools follow a consistent verb_noun pattern (get_*), which is excellent. However, tool descriptions are generic (averaging ~60 chars) and lack WHAT/WHEN/WHY context. More critically, parameter descriptions are minimal or missing entirely for optional parameters like api_key. Output schemas are not documented anywhere, the responses from Finnhub API calls are likely returned raw without structured documentation of return fields. Error handling is implicit (via exception propagation) but lacks recovery guidance. The server reads well for basic use but needs substantial refinement for agent-optimal composition and LLM reasoning.

• Document output schemas for all tools. Add to tool descriptions: 'Returns a dict with fields: [field_name (type): description]. Example: {"symbol": "AAPL", "price": 150.5, "timestamp": "2025-01-01T10:00:00Z"}'. This lets LLMs understand response structure and plan chained calls.
• Expand tool descriptions to 100-200 chars. Add WHEN/WHY context: 'Use get_stock_quote to fetch current prices for real-time charting or alert systems. Requires a valid stock symbol (e.g., AAPL). Returns price, bid, ask, and timestamp.'
• Add enum constraints for 'category' and 'metric'. Replace defaults with explicit lists: category: enum=['general', 'forex', 'crypto', 'merger'] (adjust based on Finnhub API docs). This prevents hallucination.
• Improve 'symbol' parameter guidance: 'Stock symbol (e.g., AAPL, MSFT, TSLA). Must be 1 - 5 uppercase letters or digits. Invalid symbols return an error.'
• Document pagination behavior for get_market_news: 'Returns up to 50 items. Use the min_id field from the last result as min_id in the next call to fetch older items. Iteration complete when response is empty.'
• Add error recovery guidance in tool descriptions. Example: 'If symbol is not found, try search_symbols() first to discover valid tickers.' (Requires implementing a search_symbols tool or documenting available symbols.)
• Add tool annotations to FastMCP definitions where applicable. Mark all tools with readOnlyHint=true (all are read-only). This helps agents understand tool safety without extra reasoning.
• Consider implementing a discovery/reference tool like 'get_available_markets' or 'search_symbols' to help agents discover valid inputs without brute-force guessing.