{"name":"heart_rate_zones","title":"Heart-Rate Training Zones","category":"fitness","description":"Max heart rate and the five training zones (recovery to VO2max) from age; uses the Karvonen reserve method when a resting heart rate is given.","price_usd":0.001,"input_schema":{"type":"object","properties":{"age":{"type":"integer","description":"Age in years"},"resting_hr":{"type":"integer","description":"Resting heart rate in bpm (optional, enables Karvonen method)"}},"additionalProperties":false,"required":["age"]}}