{"success":true,"calculator":"gravel","description":"Calculate tons and cubic yards of gravel needed for driveways and landscaping.","endpoint":"/api/calculate/gravel","method":"GET or POST","parameters":{"length_ft":"Area length in feet (required)","width_ft":"Area width in feet (required)","depth_in":"Gravel depth in inches (default: 4)","gravel_type":"pea-gravel | crushed-stone | river-rock | crusher-run | limestone | decomposed-granite (default: crushed-stone)"},"example_url":"/api/calculate/gravel?length_ft=20&width_ft=10&depth_in=4&gravel_type=crushed-stone"}