Single tool with minimal definition quality. Tool name 'previsao_do_tempo' lacks English verb prefix and is non-standard (Portuguese). Description is adequate (73 chars) but parameter lacks detail on format/constraints. Input schema present but minimal (single string param, no validation). No output schema documented. Critical issue: hardcoded API key in source code violates secret-injection pattern. No error handling guidance for LLM recovery. Tool does one thing (acceptable) but implementation exposes security risk.

• Rename tool to 'get_weather_forecast' (or 'get_weather') to match verb_noun convention and enable LLM intent inference from name.
• Move API key to environment variable (process.env.OPENWEATHER_API_KEY) and validate at startup. Never embed secrets in source.
• Document output schema: {city: string, temperature: number, feels_like: number, description: string, humidity: number}.
• Enhance parameter description: 'City name (2-100 characters, e.g. "São Paulo", "New York"). Use full city name; partial names may fail.'
• Implement error classification: return {error: 'city_not_found', message: '...', suggestion: 'Try search_cities() or check spelling'} vs {error: 'api_error', message: '...', retryable: true}.