Keyword Expansion

Expand a seed keyword into related keywords and search suggestions. Call the Keyword Expansion API via REST or MCP to automate SEO research.

CostRecent Avg. 39 · Range 36–42 credits / call

Try online

POST · https://api.nexscope.ai/seo/keywordExpandMCP · nexscope_seo_keyword_expand

Keyword Research

What this API does

Expand a seed keyword into related keywords and search suggestions. The request accepts keyword, language, limit, market, sources. Its documented result includes keyword, keywordDifficulty, relations.depth, relations.seed, searchVolume, language, market, requestedLimit.

Keyword Expansion API use cases

Build a keyword shortlist

To build a keyword shortlist, a search marketer submits keyword and language to Keyword Expansion. The returned keyword, keywordDifficulty, relations.depth help choose candidate search terms for further investigation.

Compare search demand signals

A search marketer uses Keyword Expansion with keyword and language to compare search demand signals. The returned keyword, keywordDifficulty, relations.depth help compare keyword demand within the requested market scope.

Plan a content or advertising test

For this workflow, a search marketer calls Keyword Expansion with keyword and language to plan a content or advertising test. The result helps select terms for a content or advertising experiment.

Keyword Expansion API FAQ

What does the Keyword Expansion API return?

Expand a seed keyword into related keywords and search suggestions. The documented output includes keyword, keywordDifficulty, relations.depth, relations.seed, searchVolume, language, market, requestedLimit. It corresponds to the supplied keyword, language, limit, market, sources. 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 Keyword Expansion API cost?

The current documented cost is Recent Avg. 39 · Range 36–42 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 Keyword Expansion API from my app or an MCP client?

Send a POST request to https://api.nexscope.ai/seo/keywordExpand 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_seo_keyword_expand. The same documented request parameters apply; use Online test to review a 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/keywordExpand

MCP method

nexscope_seo_keyword_expand

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/keywordExpand

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/keywordExpand' \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "keyword": "nexscope",
  "language": "en",
  "limit": 10,
  "market": "US",
  "sources": [
    "suggestions",
    "related"
  ]
}'

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	HTTP request completed. Check JSON code; only 0 indicates business success or acceptance.
400	Request JSON or required API parameters are invalid.
401	API key is missing, invalid, or cannot be matched to a user.
5xx	API execution or upstream service failed.

View parameters & response Try online

All categories/ Keyword Research

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

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/keywordExpand`
Auth	`Bearer API key`
Content-Type	`application/json`

Request parameters

Name	Type	Required	Description
`keyword`	`string`	required	Trimmed, at most ten whitespace-separated words. Minimum length: 1 Maximum length: 80
`language`	`string`	required	Language value used by this API operation. Allowed: en
`limit`	`integer`	optional	Limit value used by this API operation. Default: 10 Minimum: 1 Maximum: 20
`market`	`string`	required	Market value used by this API operation. Allowed: US
`sources`	`array`	optional	Sources value used by this API operation. Default: ["suggestions","related"] Minimum items: 1 Maximum items: 2
`sources[]`	`string`	required	Item in sources. Allowed: suggestions, related

Code example

{
  "keyword": "nexscope",
  "language": "en",
  "limit": 10,
  "market": "US",
  "sources": [
    "suggestions",
    "related"
  ]
}

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": {
      "items": [
        {
          "keyword": "synthetic",
          "keywordDifficulty": 9007199254740992,
          "missing": [
            {
              "field": "synthetic",
              "reason": "synthetic"
            }
          ],
          "relations": [
            {
              "depth": 1,
              "seed": "synthetic",
              "source": "synthetic"
            }
          ],
          "searchVolume": 9007199254740992
        }
      ],
      "language": "synthetic",
      "market": "synthetic",
      "requestedLimit": 1,
      "returnedCount": 1,
      "seed": "synthetic",
      "sources": [
        {
          "missingReason": "synthetic",
          "returnedCount": 1,
          "source": "synthetic",
          "status": "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`	optional	Call id value used by this API operation. Format: uuid
`data.completedAt`	`string \| integer \| null`	optional	UTC epoch milliseconds.
`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.reason`	`string`	optional	Stable reason on errors 42001 through 42011; accepted errors retain callId.
`data.requestedAt`	`string \| integer \| null`	optional	UTC epoch milliseconds.
`data.result`	`object \| null`	required	Result value used by this API operation.
`data.result.items`	`array`	optional	Items value used by this API operation.
`data.result.items[]`	`object`	required	Item in data result items.
`data.result.items[].keyword`	`string \| null`	optional	Keyword value used by this API operation.
`data.result.items[].keywordDifficulty`	`number \| null`	optional	Keyword difficulty value used by this API operation.
`data.result.items[].missing`	`array`	optional	Missing value used by this API operation.
`data.result.items[].missing[]`	`object`	required	Item in data result items[] missing.
`data.result.items[].missing[].field`	`string \| null`	optional	Field value used by this API operation.
`data.result.items[].missing[].reason`	`string \| null`	optional	Reason value used by this API operation.
`data.result.items[].relations`	`array`	optional	Relations value used by this API operation.
`data.result.items[].relations[]`	`object`	required	Item in data result items[] relations.
`data.result.items[].relations[].depth`	`integer \| null`	optional	Depth value used by this API operation.
`data.result.items[].relations[].seed`	`string \| null`	optional	Seed value used by this API operation.
`data.result.items[].relations[].source`	`string \| null`	optional	Source value used by this API operation.
`data.result.items[].searchVolume`	`integer \| null`	optional	Search volume value used by this API operation.
`data.result.language`	`string \| null`	optional	Language value used by this API operation.
`data.result.market`	`string \| null`	optional	Market value used by this API operation.
`data.result.requestedLimit`	`integer \| null`	optional	Requested limit value used by this API operation.
`data.result.returnedCount`	`integer \| null`	optional	Returned count value used by this API operation.
`data.result.seed`	`string \| null`	optional	Seed value used by this API operation.
`data.result.sources`	`array`	optional	Sources value used by this API operation.
`data.result.sources[]`	`object`	required	Item in data result sources.
`data.result.sources[].missingReason`	`string \| null`	optional	Missing reason value used by this API operation.
`data.result.sources[].returnedCount`	`integer \| null`	optional	Returned count value used by this API operation.
`data.result.sources[].source`	`string \| null`	optional	Source value used by this API operation.
`data.result.sources[].status`	`string \| null`	optional	Status value used by this API operation.
`data.retryable`	`boolean`	optional	Retryable value used by this API operation. Constant: false
`data.schemaVersion`	`string`	optional	Schema version value used by this API operation. Constant: 1.0
`data.source`	`string`	optional	Source value used by this API operation. Constant: dataforseo
`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 with PROCESSING and a callId means 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/keywordExpand/calls/{callId} \
  -H "Authorization: Bearer nk-xxxxxxxxxxxxxxxxx"

Responses

Code	Description
200	HTTP request completed. Check JSON code; only 0 indicates business success or acceptance.
400	Request JSON or required API parameters are invalid.
401	API key is missing, invalid, or cannot be matched to a user.
5xx	API execution or upstream service failed.

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_seo_keyword_expand",
    "arguments": {
      "keyword": "nexscope",
      "language": "en",
      "limit": 10,
      "market": "US",
      "sources": [
        "suggestions",
        "related"
      ]
    }
  }
}

Legacy MCP v1

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

GET / POST /mcp/legacy

Online test

Execute the current API with your API key and JSON payload. Online tests use this site's configured API environment; the Endpoint and copyable examples use the public integration address.

Uses your signed-in Nexscope session

SEO API Lab

SEO Keyword Expansion

Expand a seed keyword into related keywords and search suggestions. Call the Keyword Expansion API via REST or MCP to automate SEO research.

Live request

Estimated 19 credits / callAPI usage records

Keyword

Trimmed, at most ten whitespace-separated words.

Up to 80 characters

Language

Choose one of the supported values: en.

1 option

Limit

Value sent as the “limit” request parameter.

1–20

Market

Choose one of the supported values: US.

1 option

Sources

Value sent as the “sources” request parameter.

1–2 values

Live calls may use Data credits.

Processing result

If a request is still processing, use the returned identifier to retrieve its stored result. The tester recognizes the identifier automatically, and result queries do not spend credits.

Live response

Results

Your live result will appear here.

Complete the request fields above and run the API. No sample response is substituted.

Test with an API key or MCP

Estimated 19 credits / callAPI usage records

Try it

Send a real request with the same contract shown in the reference.

Endpoint

/seo/keywordExpand

Processing result endpoint

https://api.nexscope.ai/seo/keywordExpand/calls/{resultId}

MCP method

nexscope_seo_keyword_expand

API key*

JSON payload*

cURL

curl -X POST \
  https://api.nexscope.ai/seo/keywordExpand \
  -H "Authorization: Bearer nk-..." \
  -H "Content-Type: application/json" \
  -d '{ "keyword": "nexscope", "language": "en", "limit": 10, "market": "US", "sources": [ "suggestions", "related" ] }'

Response

No response yet. Run the request to see the response here.

Processing result

Use the identifier returned by Run request. The tester selects the correct result query automatically, and result queries do not spend credits.

Result identifier

Result response

No task result yet. Query the task to see the generated output here.

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