Single tool with acceptable definition quality. Tool name starts with verb 'get' (good convention). Description is 108 chars, well within the 10-1024 range for A+ tools. Input parameter has explicit type (string) and detailed description including regex constraint. Output schema is documented with nested structure and field descriptions. However, the parameter description exceeds typical conciseness and contains regex pattern information that should also be validated server-side. No explicit error handling guidance for malformed yearMonthCode values. The tool is READ_ONLY (appropriate), but lacks explicit idempotency marking via tool annotations.

• Add readOnlyHint: true to the tool registration to explicitly declare the tool as safe to call multiple times without side effects, enabling cached execution.
• Validate yearMonthCode format server-side before calling getMonthlyStatement(). Return a specific error like 'Invalid year-month code format. Expected format: YYYYM## (e.g., 2024M01). Got: {value}' instead of a generic 'Error: {message}'.
• Enhance error responses to guide recovery. Example: if month/year is out of range, return 'Statement not available for {yearMonthCode}. Available months are 2024M01 through 2024M12.'
• Add descriptions to all output schema fields, particularly institution.accountType, transactionAmount.currency, and balance fields, clarify what values are valid.
• Consider adding a pagination or filtering mechanism if statements can grow very large (e.g., thousands of transactions). Document the expected transaction volume and any limits.
• Separate the regex pattern constraint from the parameter description. Use the description to explain the semantic meaning ('year-month code like January 2024') and let Zod schema enforce the pattern.