Three well-defined banking tools with complete JSON schemas, clear descriptions, and proper parameter constraints. All tools have type-annotated inputs with min/max bounds and regex patterns. Descriptions are concise (40-60 chars) and action-oriented. Security-focused design with scope-based access control (ACCOUNTS_READ, TRANSACTIONS_READ, TRANSFERS_WRITE). Strengths: strict input validation enabled, proper error masking, idempotent read operations. Gaps: no output schema documentation visible in code, no error recovery guidance in descriptions, no batch operations, limited parameter descriptions (e.g., 'limit' lacks rationale for 1-100 range).

• Document output schemas inline or via docstrings. E.g., 'Returns Balance with fields: account_id (str), balance_cents (int), currency (str)'. LLMs need explicit field names to chain tools.
• Expand parameter descriptions with rationale and constraints. E.g., 'limit: Maximum transactions to return (1-100, default 20). Use higher values for historical analysis; lower for recent activity summaries.'
• Add error recovery hints to tool descriptions. E.g., 'Raises AccessDeniedError if account not owned by caller. Raises NotFoundError if account_id does not exist. Use check_balance first to verify account access.'
• Implement a confirm_transfer tool or add a dry_run parameter to transfer_between_own_accounts. Return estimated fees and final balance before committing. Prevents accidental transfers.
• Consider batch_check_balances(account_ids: List[AccountId]) and batch_transaction_history(account_ids: List[AccountId], limit: int) to reduce round-trips for multi-account queries.