Rail402 MCP defines 4 tools with clear action verbs and reasonable descriptions (avg 156 chars). All tools have input schemas with required fields and type declarations. However, parameter descriptions lack specificity on constraints, formats, and error recovery guidance. Output schemas are not documented. Error handling returns generic fail() messages without actionable recovery steps. Missing tool annotations (readOnlyHint/destructiveHint). The call_service tool accepts an untyped 'input' object, forcing LLMs to infer structure from a separate discovery call.

• Document output schemas for all tools. E.g., list_services returns {count: number, services: [{id, slug, name, description, category, priceAmount, priceCurrency, network}]}. This enables LLMs to chain calls correctly.
• Add min/max constraints to numeric parameters. E.g., limit: {type: 'number', minimum: 1, maximum: 100, description: 'Max results (default 20, range 1-100)'}.
• Enhance error messages with recovery guidance. E.g., fail('Insufficient balance: current=0.5 USDC, required=1.0. Call check_payment_status to verify recent transactions or top up wallet.').
• Add tool annotations to call_service: {destructiveHint: true} to signal that this tool charges funds and should be confirmed before execution.
• Validate and document the 'input' parameter schema for call_service. Either accept a typed object with known fields or require LLM to pass the full inputSchema from get_service_details as a constraint.