Page Loading Waterfall

See how each resource on a page loads, in order, to find slow requests. Call the Page Loading Waterfall API via REST or MCP to automate SEO research.

CostEstimated 10 credits / call

Try online

POST · https://api.nexscope.ai/seo/pageLoadingWaterfallMCP · nexscope_page_loading_waterfall

What this API does

See how each resource on a page loads, in order, to find slow requests. The request accepts pageUrl, task_id. Its documented result includes connectionMs, domCompleteMs, durationMs, interactiveMs, pageUrl, resources.durationMs, resources.endMs, resources.initiator.

Page Loading Waterfall API use cases

Investigate a website quality issue

To investigate a website quality issue, a search marketer submits pageUrl and task_id to Page Loading Waterfall. The returned connectionMs, domCompleteMs, durationMs help locate the pages or resources behind the reported issue.

Prioritize pages for technical review

A search marketer uses Page Loading Waterfall with pageUrl and task_id to prioritize pages for technical review. The returned connectionMs, domCompleteMs, durationMs help choose affected pages for the next technical investigation.

Record evidence before a site change

For this workflow, a search marketer calls Page Loading Waterfall with pageUrl and task_id to record evidence before a site change. The result helps compare saved evidence before and after a site correction.

Page Loading Waterfall API FAQ

What does the Page Loading Waterfall API return?

See how each resource on a page loads, in order, to find slow requests. The documented output includes connectionMs, domCompleteMs, durationMs, interactiveMs, pageUrl, resources.durationMs, resources.endMs, resources.initiator. It corresponds to the supplied pageUrl, task_id. Optional fields can be absent; a missing value should not be interpreted as a measured zero. Example values illustrate the response shape, rather than live account results.

How many credits does the Page Loading Waterfall API cost?

The current documented cost is Estimated 10 credits / call. This is the same cost shown at the top of this page. If a range or estimate is displayed, the final charge depends on the request. Review your available credits and the pricing page before calling the API, and check API usage records for the actual charge.

How do I call the Page Loading Waterfall API from my app or an MCP client?

Send a POST request to https://api.nexscope.ai/seo/pageLoadingWaterfall with your API key as a Bearer token and the JSON inputs shown in API integration. In a compatible MCP client such as Claude or Cursor, connect Nexscope and call nexscope_page_loading_waterfall. Use the MCP arguments shown in the MCP guide, or switch Online test to MCP to review its request before adding it to your app.

View plans and credits Connect this API with MCP

Try this API

Endpoint

https://api.nexscope.ai/seo/pageLoadingWaterfall

MCP method

nexscope_page_loading_waterfall

Step 1 of 3 · Authenticate

Authentication

All run endpoints require a user API key. Send it as a bearer token in the Authorization header.

Authorization: Bearer nk-xxxxxxxxxxxxxxxxx

Missing or invalid API keys return an authentication error. Manage keys from .

Step 2 of 3 · Send a request

POSThttps://api.nexscope.ai/seo/pageLoadingWaterfall

Run an API

Send a JSON request body using the parameters described below.

Example request

Replace YOUR_API_KEY, then run this command in your terminal.

curl -X POST 'https://api.nexscope.ai/seo/pageLoadingWaterfall' \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "pageUrl": "https://www.nexscope.ai/",
  "task_id": ""
}'

Code example

{
  "pageUrl": "https://www.nexscope.ai/",
  "task_id": ""
}

Step 3 of 3 · Inspect the result

Check the response

Read code for the request status and data for the result. Open the parameter and response reference for the full field definitions.

HTTP status codes

Code	Description
200	Default HTTP response for both success and many business errors. Only outer JSON code 0 indicates success or asynchronous acceptance; inspect data for the result.
429	Execution admission rate limit; honor Retry-After when present.
503	Execution admission is temporarily unavailable; honor Retry-After when present.
Opt-in	X-Nexscope-Http-Status: semantic maps controller-handled business errors to HTTP status on run and task routes. Pre-authentication failures, such as a missing or invalid API key (code 11209, including an incomplete or corrupted copy) or an expired website login session (code 12001), may still return HTTP 200 before this mapping. Always check the outer JSON code; malformed requests and infrastructure failures may also return non-200 HTTP responses.

View parameters & response Try online

All categories/ Website & On-Page SEO

POSThttps://api.nexscope.ai/seo/pageLoadingWaterfall

Run this API

Send a JSON request to execute this API and receive the documented response payload.

Open tester

Endpoint

Method	`POST`
Path	`https://api.nexscope.ai/seo/pageLoadingWaterfall`
Auth	`Bearer API key`
Content-Type	`application/json`

Request parameters

Name	Type	Required	Description
`pageUrl`	`string`	required	Page url value used by this API operation. Format: uri Maximum length: 2048
`task_id`	`string`	required	Task id value used by this API operation. Minimum length: 1 Maximum length: 64

Response example

Example response envelope from the documented SEO API contract.

{
  "code": 0,
  "cost": "-1",
  "data": {
    "callId": "synthetic-call",
    "completedAt": null,
    "coverage": {
      "missing": [
        {
          "field": "synthetic",
          "reason": "UPSTREAM_FIELD_MISSING"
        }
      ],
      "status": "PARTIAL"
    },
    "requestedAt": "123",
    "result": {
      "coverage": {
        "invalidItemCount": 1,
        "limit": 1,
        "maxCrawlPages": 9007199254740992,
        "offset": 1,
        "pagesCrawled": 9007199254740992,
        "providerTotal": 9007199254740992,
        "returnedCount": 1,
        "sampled": false,
        "stopReason": "synthetic",
        "truncated": false
      },
      "items": [
        {
          "connectionMs": 1.25,
          "domCompleteMs": 1.25,
          "durationMs": 1.25,
          "interactiveMs": 1.25,
          "pageUrl": "synthetic",
          "resources": [
            {
              "durationMs": 1.25,
              "endMs": 1.25,
              "initiator": "synthetic",
              "renderBlocking": false,
              "startMs": 1.25,
              "type": "synthetic",
              "url": "synthetic"
            }
          ],
          "secureConnectionMs": 1.25,
          "waitMs": 1.25
        }
      ],
      "missingFields": [
        {
          "field": "synthetic",
          "reason": "synthetic"
        }
      ],
      "source": {
        "candidateId": "synthetic",
        "collectedAt": 9007199254740992,
        "observationKind": "synthetic",
        "product": "synthetic",
        "provider": "synthetic",
        "queriedAt": 9007199254740992,
        "sourceCallId": "synthetic",
        "sourcePlanVersion": "synthetic",
        "sourceSchemaVersion": "synthetic"
      },
      "warnings": [
        "synthetic"
      ]
    },
    "schemaVersion": "synthetic",
    "source": "synthetic",
    "status": "PARTIAL",
    "usage": {
      "billingStatus": "UNAPPROVED",
      "chargedCredits": "0"
    }
  },
  "msg": null,
  "time": "2026-01-01 00:00:00",
  "traceId": "synthetic-trace",
  "ts": "9007199254740993"
}

Response fields

Name	Type	Required	Description
`code`	`integer`	required	0 is a successful envelope; inspect data.status separately. Allowed: 0, 42008, 42009
`cost`	`string`	required	Elapsed processing milliseconds; not price. -1 for non-web context.
`data`	`object`	required	Data value used by this API operation.
`data.callId`	`string \| null`	optional	Call id value used by this API operation.
`data.completedAt`	`string \| integer \| null`	optional	Completed at value used by this API operation.
`data.coverage`	`object`	optional	Coverage value used by this API operation.
`data.coverage.missing`	`array`	optional	Missing value used by this API operation.
`data.coverage.missing[]`	`object`	required	Item in data coverage missing.
`data.coverage.missing[].field`	`string`	optional	Field value used by this API operation.
`data.coverage.missing[].reason`	`string`	optional	Reason value used by this API operation.
`data.coverage.status`	`string`	optional	Status value used by this API operation.
`data.requestedAt`	`string \| integer \| null`	optional	Requested at value used by this API operation.
`data.result`	`object \| null`	required	Result value used by this API operation.
`data.result.coverage`	`object`	required	Coverage value used by this API operation.
`data.result.coverage.invalidItemCount`	`integer`	required	Invalid item count value used by this API operation. Minimum: 0
`data.result.coverage.limit`	`integer`	required	Limit value used by this API operation. Minimum: 0
`data.result.coverage.maxCrawlPages`	`integer \| null`	required	Max crawl pages value used by this API operation. Minimum: 0
`data.result.coverage.offset`	`integer`	required	Offset value used by this API operation. Minimum: 0
`data.result.coverage.pagesCrawled`	`integer \| null`	required	Pages crawled value used by this API operation. Minimum: 0
`data.result.coverage.providerTotal`	`integer \| null`	required	Provider total value used by this API operation. Minimum: 0
`data.result.coverage.returnedCount`	`integer`	required	Returned count value used by this API operation. Minimum: 0
`data.result.coverage.sampled`	`boolean`	required	Sampled value used by this API operation. Constant: true
`data.result.coverage.stopReason`	`string \| null`	required	Stop reason value used by this API operation.
`data.result.coverage.truncated`	`boolean`	required	Truncated value used by this API operation.
`data.result.items`	`array`	required	Items value used by this API operation. Maximum items: 1
`data.result.items[]`	`object`	required	Item in data result items.
`data.result.items[].connectionMs`	`number \| null`	required	Connection ms value used by this API operation. Minimum: 0
`data.result.items[].domCompleteMs`	`number \| null`	required	Dom complete ms value used by this API operation. Minimum: 0
`data.result.items[].durationMs`	`number \| null`	required	Duration ms value used by this API operation. Minimum: 0
`data.result.items[].interactiveMs`	`number \| null`	required	Interactive ms value used by this API operation. Minimum: 0
`data.result.items[].pageUrl`	`string`	required	Page url value used by this API operation. Maximum length: 2048
`data.result.items[].resources`	`array`	required	Resources value used by this API operation. Maximum items: 200
`data.result.items[].resources[]`	`object`	required	Item in data result items[] resources.
`data.result.items[].resources[].durationMs`	`number \| null`	required	Duration ms value used by this API operation. Minimum: 0
`data.result.items[].resources[].endMs`	`number \| null`	required	End ms value used by this API operation. Minimum: 0
`data.result.items[].resources[].initiator`	`string \| null`	required	Initiator value used by this API operation. Maximum length: 4096
`data.result.items[].resources[].renderBlocking`	`boolean \| null`	required	Render blocking value used by this API operation.
`data.result.items[].resources[].startMs`	`number \| null`	required	Start ms value used by this API operation. Minimum: 0
`data.result.items[].resources[].type`	`string \| null`	required	Type value used by this API operation.
`data.result.items[].resources[].url`	`string`	required	Url value used by this API operation. Maximum length: 2048
`data.result.items[].secureConnectionMs`	`number \| null`	required	Secure connection ms value used by this API operation. Minimum: 0
`data.result.items[].waitMs`	`number \| null`	required	Wait ms value used by this API operation. Minimum: 0
`data.result.missingFields`	`array`	required	Missing fields value used by this API operation. Maximum items: 10000
`data.result.missingFields[]`	`object`	required	Item in data result missingFields.
`data.result.missingFields[].field`	`string`	required	Field value used by this API operation.
`data.result.missingFields[].reason`	`string`	required	Reason value used by this API operation.
`data.result.source`	`object`	required	Source value used by this API operation.
`data.result.source.candidateId`	`string`	required	Candidate id value used by this API operation. Constant: MD-PW-11
`data.result.source.collectedAt`	`integer \| null`	required	Collected at value used by this API operation. Minimum: 0 Maximum: 9007199254740991
`data.result.source.observationKind`	`string`	required	Observation kind value used by this API operation. Constant: CRAWL_SAMPLE
`data.result.source.product`	`string`	required	Product value used by this API operation. Constant: on_page
`data.result.source.provider`	`string`	required	Provider value used by this API operation. Constant: DATAFORSEO
`data.result.source.queriedAt`	`integer`	required	Queried at value used by this API operation. Minimum: 0 Maximum: 9007199254740991
`data.result.source.sourceCallId`	`string \| null`	required	Source call id value used by this API operation.
`data.result.source.sourcePlanVersion`	`string \| null`	required	Source plan version value used by this API operation.
`data.result.source.sourceSchemaVersion`	`string \| null`	required	Source schema version value used by this API operation.
`data.result.warnings`	`array`	required	Warnings value used by this API operation. Maximum items: 1000
`data.result.warnings[]`	`string`	required	Item in data result warnings.
`data.schemaVersion`	`string \| null`	optional	Schema version value used by this API operation.
`data.source`	`string \| null`	optional	Source value used by this API operation.
`data.status`	`string`	optional	Status value used by this API operation. Allowed: SUCCESS, PARTIAL, EMPTY, PROCESSING, UNKNOWN, FAILED
`data.usage`	`object \| null`	optional	Usage value used by this API operation.
`data.usage.billingStatus`	`string \| null`	optional	Billing status value used by this API operation.
`data.usage.chargedCredits`	`string \| integer \| null`	optional	Charged credits value used by this API operation.
`msg`	`string \| null`	required	Available upstream msg/errmsg/message is preferred for success and failure; Chinese is translated to English. Missing successful message is null. Platform-only errors and task states use platform English. Message text never determines success or retry.
`time`	`string`	required	yyyy-MM-dd HH:mm:ss
`traceId`	`string \| null`	required	Trace id value used by this API operation.
`ts`	`string`	required	Epoch milliseconds; global long serializer.

Accepted processing response

code 0 confirms acceptance. Use data.callId to query the same request; processing is not completion.

Name	Type	Required	Description
`code`	`integer`	required	0 is a successful envelope; inspect data.status separately. Constant: 0
`cost`	`string`	required	Elapsed processing milliseconds; not price. -1 for non-web context.
`data`	`object`	required	Data value used by this API operation.
`data.callId`	`string \| null`	required	Call id value used by this API operation.
`data.reason`	`string`	required	Reason value used by this API operation. Constant: IN_PROGRESS
`data.retryable`	`boolean`	optional	Retryable value used by this API operation.
`data.status`	`string`	required	Status value used by this API operation. Constant: PROCESSING
`data.taskId`	`string \| null`	optional	Task id value used by this API operation.
`msg`	`string \| null`	required	Available upstream msg/errmsg/message is preferred for success and failure; Chinese is translated to English. Missing successful message is null. Platform-only errors and task states use platform English. Message text never determines success or retry.
`time`	`string`	required	yyyy-MM-dd HH:mm:ss
`traceId`	`string \| null`	required	Trace id value used by this API operation.
`ts`	`string`	required	Epoch milliseconds; global long serializer.

Error response

Name	Type	Required	Description
`code`	`integer`	required	0 is a successful envelope; inspect data.status separately.
`cost`	`string`	required	Elapsed processing milliseconds; not price. -1 for non-web context.
`data`	`object`	required	Data value used by this API operation.
`data.callId`	`string \| null`	required	Call id value used by this API operation.
`data.reason`	`string \| null`	required	Reason value used by this API operation.
`data.retryable`	`boolean`	optional	Retryable value used by this API operation.
`data.status`	`string \| null`	required	Status value used by this API operation.
`data.taskId`	`string \| null`	optional	Task id value used by this API operation.
`msg`	`string \| null`	required	Available upstream msg/errmsg/message is preferred for success and failure; Chinese is translated to English. Missing successful message is null. Platform-only errors and task states use platform English. Message text never determines success or retry.
`time`	`string`	required	yyyy-MM-dd HH:mm:ss
`traceId`	`string \| null`	required	Trace id value used by this API operation.
`ts`	`string`	required	Epoch milliseconds; global long serializer.

Retrieve a processing result

A response withPROCESSING and a callIdmeans the result is still being prepared. Use the result query below with the returned identifier. This lookup reads the stored result and does not spend credits.

curl -X GET https://api.nexscope.ai/seo/pageLoadingWaterfall/calls/{callId} \
  -H "Authorization: Bearer nk-xxxxxxxxxxxxxxxxx"

Responses

Code	Description
200	Default HTTP response for both success and many business errors. Only outer JSON code 0 indicates success or asynchronous acceptance; inspect data for the result.
429	Execution admission rate limit; honor Retry-After when present.
503	Execution admission is temporarily unavailable; honor Retry-After when present.
Opt-in	X-Nexscope-Http-Status: semantic maps controller-handled business errors to HTTP status on run and task routes. Pre-authentication failures, such as a missing or invalid API key (code 11209, including an incomplete or corrupted copy) or an expired website login session (code 12001), may still return HTTP 200 before this mapping. Always check the outer JSON code; malformed requests and infrastructure failures may also return non-200 HTTP responses.

Data source, freshness, and limitations

Source, freshness, coverage, rate limits, and estimation notes are not specified in this API definition unless they appear in the request or response field documentation above. Do not assume official marketplace data or real-time freshness when it is not explicitly documented.

Step 1 of 2 · Connect your MCP client

MCP

V2 recommended

Connect remote agents through the standard MCP 2025-11-25 Streamable HTTP endpoint. Use OAuth 2.1 Authorization Code with PKCE, or an API key for compatibility.

POST https://api.nexscope.ai/mcp
MCP-Protocol-Version: 2025-11-25
Content-Type: application/json

Authentication

OAuth clients request the mcp:tools scope. The endpoint's 401 response advertises protected-resource metadata for authorization discovery.

Step 2 of 2 · Call the tool

Call a tool

{
  "jsonrpc": "2.0",
  "id": "tool-call-1",
  "method": "tools/call",
  "params": {
    "name": "nexscope_page_loading_waterfall",
    "arguments": {
      "pageUrl": "https://www.nexscope.ai/",
      "task_id": ""
    }
  }
}

Legacy MCP v1

Existing API-key clients can continue using the compatibility endpoint. New integrations should use MCP v2.

GET / POST /mcp/legacy

What can you do with this API?

Data explained and practical use cases

AI Guide

Question

What loading data can Page Loading Waterfall provide, and how might I use it?

AI answer

Page Loading Waterfall shows page-level timing and the order and duration of resource requests for a sampled page. It can help you locate requests that coincide with slow loading.

Data category	Documented fields	What the values mean
Page timing	`durationMs`, `domCompleteMs`, `interactiveMs`	Overall loading duration and milestones for DOM completion and interactivity, in milliseconds.
Connection timing	`connectionMs`, `secureConnectionMs`, `waitMs`	Time spent in connection, secure connection, and waiting phases, when available.
Resource identity	`resources.url`, `resources.type`, `resources.initiator`	Which resource loaded, its type, and what initiated it.
Resource sequence	`resources.startMs`, `resources.endMs`, `resources.durationMs`	When each request started and ended, and how long it took.
Rendering impact	`resources.renderBlocking`	Whether a resource is identified as blocking rendering.
Sample coverage	`coverage.sampled`, `coverage.truncated`, `coverage.returnedCount`, `missingFields`	Indicates that the result is a sample, whether it was cut short, how many page items were returned, and which values are missing.

Find a long-running script or image request that overlaps a slow page load.
- Prompt example: “I am reviewing an ecommerce website. Could you find a long-running script or image request that overlaps a slow page load? Show matching records and source links where the API provides them; ask me for any required identifier or filter.”
Compare connection and waiting time to decide which part of a request merits investigation.
- Prompt example: “I am reviewing an ecommerce website. Could you compare connection and waiting time to decide which part of a request merits investigation? Show the returned values behind the comparison, and mark missing data.”
Identify render-blocking resources to prioritize a page-performance review.
- Prompt example: “I am reviewing an ecommerce website. Could you identify render-blocking resources to prioritize a page-performance review? Show the returned values behind the comparison, and mark missing data.”
Check coverage.truncated and missingFields before treating the waterfall as a complete account of page activity.
- Prompt example: “I am reviewing an ecommerce website. Could you check coverage.truncated and missingFields before treating the waterfall as a complete account of page activity? Show the relevant returned evidence and tell me what input you need from me.”

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