curl --request POST \
  --url https://api.iotools.cloud/v1/tool/earthing-grid-resistance-estimator \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "soilResistivity": "100",
  "gridArea": "100",
  "conductorLength": "200",
  "burialDepth": "0.5",
  "rodCount": "4",
  "rodLength": "3",
  "targetResistance": "25"
}
'

{
  "tool": "earthing-grid-resistance-estimator",
  "tool_version": "1.0.2",
  "outputs": {
    "results": [
      {
        "quantity": "Soil resistivity (ρ)",
        "value": "100 Ω·m"
      },
      {
        "quantity": "Grid area (A)",
        "value": "100 m²"
      },
      {
        "quantity": "Total buried conductor length (L)",
        "value": "212 m (200 grid + 12 rods)"
      },
      {
        "quantity": "Burial depth (h)",
        "value": "0.5 m"
      },
      {
        "quantity": "Estimated earthing resistance (Rg)",
        "value": "4.53521 Ω"
      },
      {
        "quantity": "Target resistance (25 Ω)",
        "value": "Meets target"
      }
    ],
    "breakdown": "Rg = ρ × [ 1/L + 1/√(20A) × (1 + 1/(1 + h√(20/A))) ]  (IEEE Std 80 Sverak equation)\nL = conductor length + rods × rod length = 200 + 4 × 3 = 212 m\n1/L = 0.00471698\n1/√(20A) × (1 + 1/(1 + h√(20/A))) = 0.0406351\nRg = 100 × (0.00471698 + 0.0406351) = 4.53521 Ω\n4.53521 Ω is at or below the 25 Ω target.\nSingle-layer-soil screening estimate only — not a substitute for a full grounding/fault study."
  },
  "credits_used": 5,
  "credits_remaining": null
}