Yahoo Finance MCP demonstrates good definition quality with consistent verb-based naming, documented schemas using Zod, and descriptive tool summaries. All 6 tools follow a clear pattern (get_*, search_*) and include input parameter constraints via enums and length validation. However, output schemas lack documentation, responses are JSON-stringified text rather than structured typed objects, and error handling is minimal (returns error text in content field without recovery guidance). Tool descriptions are adequate (100-180 chars) but lack dependency hints or prerequisites. Parameter descriptions exist but could be more explicit about format constraints and valid ranges.

• Refactor response objects from JSON-stringified text to structured typed output. Define explicit return schema for each tool (e.g., get_quote returns {symbol, name, price, change, changePercent, volume, ...} instead of JSON string). This enables LLM field extraction and tool chaining without text parsing.
• Add recovery guidance to error messages. E.g., 'Invalid ticker: AAA123. Valid tickers are 1-10 alphanumeric characters (usually uppercase, e.g., AAPL, GOOGL). Try search_symbols("Apple") to find valid symbols.'
• Include format constraints in parameter descriptions. Update 'symbol' description to: 'Stock ticker symbol in uppercase letters (e.g., AAPL, GOOGL, MSFT). 1-10 characters. Use search_symbols() if you only have a company name.'
• Add pagination support to search_symbols and get_news. Accept optional 'limit' (default 20, max 50) and 'offset' parameters. Return total_results count and next_offset to enable browsing large result sets.
• Standardize enum descriptions. For get_financials 'statement' param, update description to list enum values: 'Type of financial statement: income (income statement), balance (balance sheet), or cashflow (cash flow statement).'
• Add dependency hints to tool descriptions. E.g., get_quote: 'Get real-time stock quote data. Call search_symbols() first if you only have a company name. Note: some international markets may have limited real-time data.'
• Document that Yahoo Finance may be rate-limited or regionally restricted. Add note to server description or error messages when APIs are unavailable.