curl --request POST \
  --url https://api.iotools.cloud/v1/tool/partial-derivative-calculator \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "f": "x^2*y + sin(x*y)",
  "variable": "x",
  "order": "1"
}
'

{
  "tool": "partial-derivative-calculator",
  "tool_version": "1.0.2",
  "outputs": {
    "derivative": "y * (2 * x + cos(x * y))",
    "evaluated": "— enter x, y to evaluate",
    "steps": "f(x, y) = x^2*y + sin(x*y)\nDifferentiate w.r.t. x (pass 1 of 1): y * (2 * x + cos(x * y))\n∂f/∂x = y * (2 * x + cos(x * y))"
  },
  "credits_used": 5,
  "credits_remaining": null
}