Single tool with clear naming (exchange_rate) and complete input schema using Zod. Description is adequate (194 chars, within baseline 34-392 range). All three parameters have type definitions and descriptions. However, output schema is not documented, the tool returns JSON via text content without a formal schema declaration. Error handling is basic (try-catch with generic message). No parameter constraints (enums, ranges) despite accepting currency codes that should be validated. Missing guidance on supported currencies, date format validation, and recovery steps for API failures.

• Add formal output schema documentation: {baseCurrency: string, targetCurrency: string, date: string (ISO 8601), rate: number}. Include in tool description or as a separate schema field.
• Validate currency codes against Norges Bank's supported list. Either hardcode an enum of valid currencies or fetch and cache the list at startup. Return 'Invalid currency: USD. Supported: NOK, EUR, GBP, JPY, ...' on mismatch.
• Enhance error messages with recovery guidance: 'Currency pair USD/XYZ not available from Norges Bank. Try a major currency (EUR, GBP, JPY, SEK). Or call with date parameter to check historical availability.'
• Add regex pattern validation for date parameter: ^\d{4}-\d{2}-\d{2}$ with description 'Date in YYYY-MM-DD format (e.g., 2024-01-15). Defaults to today if omitted.'
• Document API constraints in tool description: 'Retrieves exchange rates from Norges Bank API (Norwegian central bank). Supports major currencies relative to NOK. Historical rates available back to [date]. Returns rate as of specified date or latest available.'