Server has 3 tools with generally good structure. Tool names follow verb_noun pattern (opendtu_get_*, opendtu_set_*). Descriptions are present and moderately detailed (100-200 chars each), written in German. All tools have input schemas with type definitions and parameter descriptions. However, there are critical gaps: (1) Output schemas are NOT documented, tools return strings only, making it unclear what the LLM receives and how to chain calls; (2) German-language descriptions limit accessibility for non-German speakers; (3) Error handling is basic, no recovery guidance or categorization; (4) Tool #1 (opendtu_get_inverters) has empty input schema but no documentation of output structure; (5) Tool #3 (opendtu_set_limit) has a destructive WRITE risk but no confirmation/dry-run pattern. Tool annotations are present (readOnlyHint, destructiveHint, idempotentHint) which is a positive signal.

• Add formal output schemas for all three tools. Example for opendtu_get_inverters: Document that it returns an array of objects with fields: {serial: string, name: string, reachable: bool, power_current_w: float, power_max_w: float, limit_percent: int, limit_absolute_w: int}. Include this in the tool description or as a separate response schema comment.
• Translate all descriptions to English and consider adding German as a secondary language. Format: 'List all configured inverters with live data. Returns an overview of all OpenDTU inverters including serial number, name, reachability status, current power output, and configured power limits. [German: Listet alle konfigurierten Wechselrichter...]'
• Implement a dry-run mode for opendtu_set_limit. Add an optional 'dry_run: bool' parameter (default false) that returns the predicted change without applying it. For destructive limit_type values (256, 257), require explicit confirmation or dry-run first. Example: 'This would set a persistent (EEPROM) limit. Call with dry_run=true first to preview, then confirm.'
• Enhance error handling in _handle_error to return structured error objects with a 'category' field: retryable (network, timeout), user_fixable (bad serial, auth), or fatal (API version mismatch). Example: {'error': 'Invalid serial', 'category': 'user_fixable', 'suggestion': 'Try one of these serials: 114181800001, 114181800002'}
• Add result limiting and pagination guidance. For opendtu_get_inverters and opendtu_get_limit_status, document maximum results returned (e.g. '(Note: Limited to first 50 inverters; contact server admin for larger deployments.') and describe any available filtering options.