Single tool with significant definition gaps. Tool name 'visual_crossing_history' lacks action verb prefix (should be 'get_historical_weather' or 'search_weather_history'). Description is 287 chars (within range) but lacks clarity on WHEN to use it vs alternatives, prerequisites, or return structure. Input schema present with 4 parameters, all with descriptions, but parameters lack type constraints (enums for unit_of_measure, format specs for dates). No output schema documented, LLM cannot predict response structure. No error handling guidance; bare empty dict {} on failure tells agent nothing. No pagination despite potentially large result sets. Violates pattern:tool (verb naming), pattern:tool-description (incomplete context), pattern:constrained-input (unit_of_measure should be enum), pattern:response-shaper (output undocumented).

• Rename tool to 'get_historical_weather' or 'search_weather_history' to start with action verb and clarify intent.
• Document output schema explicitly: 'Returns dict with ISO 8601 date strings as keys, each mapping to object with fields: temperature (float), max_temperature (float), min_temperature (float), precipitation (float), solar_radiation (float), humidity (float), cloud_cover (float), snow_depth (float), weather_type (string), weather_conditions (string), heat_index (float), windchill (float).'
• Change unit_of_measure parameter to enum: {"type": "string", "enum": ["metric", "us"], "description": "Unit system for temperature and precipitation (metric=Celsius/mm, us=Fahrenheit/inches)"}.
• Add date format specification to start_date and end_date: 'ISO 8601 format (YYYY-MM-DD) or datetime (YYYY-MM-DDTHH:MM:SS)'.
• Replace empty dict error response with structured error: raise exception with message like 'Failed to fetch weather data: {status_code} {reason}. Verify location name is valid and dates are in YYYY-MM-DD format.' Include retry guidance.