Yahoohoo demonstrates solid tool definition practices with 18 well-structured tools covering financial data and crypto markets. All tools have descriptions (avg 120 chars), input schemas with Zod validation, and clear parameter types. Naming follows verb_noun convention (yahoo_search, crypto_prices, analyze). However, several tools lack parameter descriptions in the schema (e.g., crypto_trending, crypto_global have empty input objects), and output schemas are not formally documented. Error handling is minimal, no recovery guidance or actionable error messages visible. The analyze tool is complex but lacks clear documentation of its recursive behavior and output structure. Tool composition is good (single responsibility), but some tools could benefit from richer parameter constraints and clearer chaining documentation.

• Add formal output schema documentation for all tools. Use JSDoc or inline comments to describe return object structure, field types, and pagination (if applicable). Example: 'Returns {quotes: Array<{symbol, price, change, timestamp}>, errors?: Array<{symbol, reason}>}'.
• Document crypto_trending and crypto_global parameters explicitly. Even if they accept no parameters, add a note: 'This tool accepts no parameters. Call it to fetch current trending cryptocurrencies.' Avoid empty input schemas.
• Implement error handling with recovery guidance. When a symbol is not found, return: 'Symbol "XYZ" not found. Try yahoo_search("XYZ") to find the correct symbol.' When API rate limits are hit, return: 'Rate limit exceeded. Retry in 60 seconds.'
• Add tool annotations to the MCP schema. Mark all tools with readOnlyHint=true since they are all READ_ONLY. This signals to agents that these tools are safe to call speculatively without side effects.
• Clarify the analyze tool's behavior: document the output structure (metrics, correlation_matrix, pairwise fields), explain when recursion occurs, and provide examples of reasoningMode='rlm' vs 'deterministic' use cases.

Inferred effective spec: 2025-06-18+.

• Relies on Logging (deprecated) - log to stderr or use OpenTelemetry