Three tools with explicit schemas and descriptions, but significant gaps in parameter documentation and output schema clarity. get_invoice and refund have clear names and basic descriptions (READ_ONLY/DESTRUCTIVE hints present), but lack output schema documentation. echo has a well-structured input schema with three typed parameters, each with descriptions. However, no tool documents what it returns, forcing LLMs to infer output structure. Parameter descriptions are minimal (10-20 chars) and lack format/constraint guidance. Tool descriptions are adequate (20-50 chars) but fall short of the 50-200 char LLM-optimized baseline. No error handling guidance or recovery paths documented.

• Document output schemas for all tools. Example for get_invoice: 'Returns {id: string, email: string (redacted), amount: number}'. This enables LLMs to chain tools correctly.
• Expand parameter descriptions to 50-100 chars with format/constraint details. E.g., 'invoice_id: The invoice identifier (format: INV-NNNNNN, e.g., INV-123456)' instead of 'The invoice identifier'.
• Add error handling guidance to tool descriptions. E.g., 'If invoice not found, returns 404 with available invoice IDs. Retry with a different ID or call list_invoices() first.'
• Implement confirmation pattern for refund tool. Add a dry_run parameter (boolean, default=true) so agents can preview refund impact before committing.
• Expand tool descriptions to 100-150 chars explaining when to use each. E.g., 'get_invoice: Retrieve full invoice details including amount, email, and dates. Use this before refunding to verify the invoice exists and amount is correct.'