mcp-stockscreen demonstrates solid tool naming and schema coverage, with clear HTTP transport and basic error handling. Tool names follow verb_noun patterns (run_stock_screen, get_stock_news, manage_watchlist, get_screening_result). All tools have input schemas with proper JSON Schema type definitions and descriptions. However, output schemas are undocumented, ResponseEnvelope type is returned but its structure is not formally specified in the code review. Parameter descriptions are present but some lack constraint clarity (e.g., 'criteria' param in run_stock_screen is documented as 'object' with no guidance on allowed nested fields per screen_type). Error handling returns ToolError with messages, but lacks recovery guidance and error classification. Security is strong (validates watchlist/result names with regex patterns, no secret parameters exposed). Tool composition is good, each tool has a single responsibility and uses symbol/name parameters that match natural identifiers. Comparison to baseline: 4 tools with 4.5 avg params each (within p10-p90 range). Tool names avg ~19 chars (within 10-27 baseline). Descriptions present but average ~120 chars, shorter than baseline 194 chars, some lack detail on when to use vs similar tools.

• Add formal output schema documentation for ResponseEnvelope. Document all top-level fields and their types (e.g., 'matches: array of {symbol: string, details: object}', 'rejected: array of {symbol: string, reasons: array[string]}').
• For run_stock_screen's 'criteria' parameter, provide a nested schema or enum-like guidance: 'For technical: {indicator: string, value: number}; for fundamental: {metric: string, threshold: number}; etc.'
• Enhance error messages with error classification and recovery hints. Example: 'Yahoo Finance request failed after retries (retryable). Try again or check your ticker symbol.' instead of raw exception text.
• Expand tool descriptions to 100-150 chars with 'when to use' context. Example for get_stock_news: 'Fetch recent news articles for a single ticker symbol. Use this for quick news lookup; use run_stock_screen with news criteria to filter news across a portfolio.'
• Update manage_watchlist schema: use 'required' array at the action level, or split into separate create_watchlist, update_watchlist, delete_watchlist, and get_watchlist tools for clarity.
• Document the RequestEnvelope/ResponseEnvelope structure in a README or schema file so agents and developers understand the response format without reading implementation code.