Website Page Speed Test & Core Web Vitals

{
  "type": "object",
  "required": [
    "url"
  ],
  "properties": {
    "url": {
      "type": "string"
    },
    "strategy": {
      "type": "string",
      "description": "mobile or desktop (default: mobile)"
    }
  },
  "additionalProperties": false
}

{
  "type": "object",
  "properties": {
    "grade": {
      "type": "string",
      "description": "A letter grade derived from performance_score, e.g. 'C' at 54, 'A' at 100."
    },
    "metrics": {
      "type": "object",
      "properties": {
        "fcp_ms": {
          "type": "number",
          "description": "First Contentful Paint, in milliseconds."
        },
        "lcp_ms": {
          "type": "number",
          "description": "Largest Contentful Paint, in milliseconds."
        },
        "tbt_ms": {
          "type": "number",
          "description": "Total Blocking Time, in milliseconds."
        },
        "ttfb_ms": {
          "type": "number",
          "description": "Time to First Byte, in milliseconds."
        },
        "cls_score": {
          "type": "number",
          "description": "Cumulative Layout Shift score (unitless, typically 0 to low single digits). Observed 0 and 0.001."
        },
        "speed_index": {
          "type": "number",
          "description": "Speed Index score, in milliseconds."
        }
      },
      "description": "Core Web Vitals and related timing metrics, all in milliseconds unless noted.",
      "additionalProperties": true
    },
    "strategy": {
      "type": "string",
      "description": "The testing strategy actually used, e.g. 'mobile' or 'desktop', echoed back."
    },
    "diagnostics": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "title": {
            "type": "string"
          },
          "description": {
            "type": "string"
          },
          "displayValue": {
            "type": "string",
            "description": "A short human-readable summary value, e.g. '2.1 s' or 'Est savings of 12 KiB'."
          }
        },
        "additionalProperties": true
      },
      "description": "Additional diagnostic findings without a direct time-savings estimate. Observed empty on a page that already scored 100 (wikipedia.org desktop) -- an empty array means no diagnostics were found, not an error."
    },
    "opportunities": {
      "type": "array",
      "items": {
        "type": "object",
        "properties": {
          "title": {
            "type": "string"
          },
          "savings_ms": {
            "type": "number",
            "description": "Estimated milliseconds saved if addressed."
          },
          "description": {
            "type": "string"
          }
        },
        "additionalProperties": true
      },
      "description": "Prioritized suggestions with an estimated time savings. Observed empty on a page that already scored 100 (wikipedia.org desktop) -- an empty array means no opportunities were found, not an error."
    },
    "performance_score": {
      "type": "number",
      "description": "Overall performance score, 0 to 100. Observed 54 (mobile, google.com) and 100 (desktop, wikipedia.org)."
    }
  },
  "description": "The page speed test result, as returned at routing.responseResultPath ($.output).",
  "additionalProperties": true
}