curl --request POST \
  --url https://api.iotools.cloud/v1/tool/hazen-williams-calculator \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "unitSystem": "si",
  "pipeDiameter": "150",
  "pipeLength": "500",
  "flowRate": "20",
  "hazenC": "130"
}
'

{
  "tool": "hazen-williams-calculator",
  "tool_version": "1.0.2",
  "outputs": {
    "results": [
      {
        "metric": "Velocity",
        "value": "1.132 m/s"
      },
      {
        "metric": "Head loss",
        "value": "4.769 m"
      },
      {
        "metric": "Hydraulic slope",
        "value": "0.9537%"
      }
    ],
    "summary": "V = 1.13 m/s · hf = 4.77 m over 500 m"
  },
  "credits_used": 5,
  "credits_remaining": null
}