HC3 MCP Server has 18 tools with basic schemas and descriptions, but significant gaps limit production readiness. All tools have descriptions (10-100 chars, mostly adequate) and input schemas with type definitions. However, output schemas are completely undocumented, LLMs cannot predict response structure for chaining. Parameter descriptions are minimal (5-30 chars) and lack actionable constraints. No enum constraints despite many parameters accepting fixed sets (e.g., 'interval' in get_energy_data). Error handling is absent, no recovery guidance, no categorization. Security concerns: credentials passed via environment variables (good), but no audit logging or permission gates visible. Tool composition is reasonable (single responsibility), but missing pagination for list tools (get_devices, get_scenes, get_users could return hundreds of items). No tool annotations (readOnlyHint, destructiveHint) despite clear read/write distinction. Average tool score: 52/100.

• Document output schema for every tool. Example: get_devices should return {devices: [{id, name, roomId, type, state, ...}], total: number}. Use JSON Schema in tool definition.
• Expand parameter descriptions to 50-100 chars with constraints. E.g., 'interval: Time period for energy data (hour, day, week, month, year). Default: day.' instead of just 'Time interval (hour, day, week, month, year)'.
• Add pagination to list tools: get_devices(limit=20, offset=0) → {devices: [...], total: 150, hasMore: true}. Cap default limit at 20-50 items.
• Add error handling: catch API errors and return structured {error: {code, message, recovery_hint}}. E.g., 'Device not found. Try get_devices() to list available devices.'
• Add tool annotations in schema: readOnlyHint for get_* tools, destructiveHint for control_device/modify_device/run_scene/set_global_variable/set_home_status, idempotentHint for safe retries.