Market Intel MCP demonstrates solid definition quality with complete input/output schemas for all 5 tools, clear descriptions (avg 156 chars), and proper parameter typing. All tools follow verb_noun naming (fx_rates, fx_convert, fx_historical, fx_timeseries, fx_currencies). However, several parameters lack descriptions (e.g., fx_convert.amount has no description in inputSchema despite being in DK_AD patch), output schemas are incomplete for 3 of 5 tools (fx_convert, fx_historical, fx_timeseries missing outputSchema), and error handling is not documented. The codebase shows defensive validation (isRatesPayload, isCurrenciesPayload) but errors are not surfaced to LLMs with recovery guidance.

• Add outputSchema to fx_convert, fx_historical, and fx_timeseries. Include fields: base (string), date (string YYYY-MM-DD), rates (object), source (string), and for fx_convert add: amount (number), from (string), to (string), result (number).
• Move fx_convert.amount description from DK_AD patch into the inputSchema directly: {"type": "number", "description": "Amount in the 'from' currency to convert. Send it as a number, not a string."}
• Add error handling section to each tool description: 'Returns error if currency code is invalid (not 3 uppercase letters), date is malformed, or upstream ECB API is unavailable. Retry with valid inputs or check https://frankfurter.dev status.'
• Document rate limits in tool descriptions: 'This server enforces a 100-call/day limit per client. Calls beyond the limit return HTTP 429. Plan multi-step workflows to stay within quota.'
• Standardize parameter requirements: decide whether 'symbols' should be required or optional across fx_rates, fx_historical, and fx_timeseries, and document the rationale in descriptions.

Inferred effective spec: 2025-06-18+.

• Relies on Stateful initialize / Mcp-Session-Id (removed; protocol is stateless) - make each request self-contained