Single tool with reasonable naming and input schema, but critical gaps in descriptions, output documentation, and error handling. The tool name 'decode_vin_batch' correctly uses verb_noun pattern (decode_*), and the input schema uses Zod with proper constraints (minItems:1, maxItems:50). However, the tool description is minimal (21 chars) and lacks context about when to use it vs alternatives. The output schema is not documented, the tool returns raw JSON as a stringified blob without a formal schema definition. Parameter description is adequate but generic. Error handling is present but not actionable (generic error messages with no recovery guidance). No parameter validation guidance provided. The implementation lacks idempotent/readonly hints, making it unclear to agents whether this tool is safe to retry.

• Add formal output schema: document that success responses return { success: boolean, totalProcessed: number, successfulDecodes: number, errors: number, results: [{vin, year?, make?, model?, gvwr?, bodyStyle?, isCommercialTruck}, ...], errorDetails: [{vin, error}, ...] }. Make clear which fields are optional.
• Expand tool description to 50-150 characters with actionable context: 'Decode commercial truck VINs (up to 50 per request) to extract year, make, model, and GVWR for insurance underwriting. Returns decoded vehicle data and identifies commercial trucks by manufacturer WMI codes. Useful for fleet vehicle intake forms.'
• Enhance 'vins' parameter description: 'Array of Vehicle Identification Numbers (VINs) to decode. Each VIN must be exactly 17 characters (alphanumeric, no spaces). Supports major truck manufacturers: Freightliner, Mack, Peterbilt, Kenworth, International, Volvo. Up to 50 VINs per request.'
• Implement actionable error messages: instead of 'Decoding error: <generic>', return 'Invalid VIN format for entry 3 (INVALID123ABC): VINs must be exactly 17 alphanumeric characters. Skipped. Processing remaining 49 VINs.'
• Add tool annotations via FastMCP if available (readOnlyHint: true, idempotentHint: true) to signal that this tool is safe to retry without side effects.
• Document response structure in tool description with example: 'Returns { success, totalProcessed, successfulDecodes, results: [{ vin, year, make, model, isCommercialTruck, ...}], errorDetails: [{ vin, error }] }. Each VIN may return partial data (e.g., year and make but not model) if database lacks full record.'