curl --request POST \
  --url https://api.iotools.cloud/v1/tool/column-slenderness-calculator \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "endCondition": "pinned-pinned",
  "unbracedLength": "4",
  "material": "steel-a36",
  "sectionMode": "direct",
  "radiusOfGyration": "50",
  "crossSectionArea": "5000"
}
'

{
  "tool": "column-slenderness-calculator",
  "tool_version": "1.0.2",
  "outputs": {
    "status": "λ = 80.00 vs. Cc = 125.7 — short/intermediate column. Fcr = 199.3 MPa, Pcr = 996.7 kN.",
    "results": [
      {
        "property": "Effective Length Factor (K)",
        "value": "1.000"
      },
      {
        "property": "Effective Length (KL)",
        "value": "4,000 mm (4.000 m)"
      },
      {
        "property": "Radius of Gyration (r)",
        "value": "50.00 mm"
      },
      {
        "property": "Slenderness Ratio (λ = KL/r)",
        "value": "80.00"
      },
      {
        "property": "Critical Slenderness Ratio (Cc)",
        "value": "125.7"
      },
      {
        "property": "Classification",
        "value": "Short/intermediate column (λ < Cc)"
      },
      {
        "property": "Buckling Mode",
        "value": "Inelastic buckling governs (Johnson parabola) — yielding and buckling interact."
      },
      {
        "property": "Critical Buckling Stress (Fcr)",
        "value": "199.3 MPa"
      },
      {
        "property": "Cross-Sectional Area",
        "value": "5,000 mm²"
      },
      {
        "property": "Critical Buckling Load (Pcr)",
        "value": "996.7 kN"
      },
      {
        "property": "Elastic Modulus Used",
        "value": "200.0 GPa"
      },
      {
        "property": "Yield Strength Used",
        "value": "250.0 MPa"
      },
      {
        "property": "Note",
        "value": "Textbook Euler-Johnson estimate for a preliminary check only — not a substitute for a code-based design capacity (apply your governing code's resistance/safety factors separately)."
      }
    ]
  },
  "credits_used": 5,
  "credits_remaining": null
}