> ## Documentation Index
> Fetch the complete documentation index at: https://hexagraph-docs.voyla.in/llms.txt
> Use this file to discover all available pages before exploring further.

# Topic

> Retrieve detailed metadata for a single research topic cluster by its HX_T identifier.

Retrieves a granular research topic cluster (Level 3 leaf node in the taxonomy) by its `HX_T` identifier.

### Path Parameters

<ParamField path="id" type="string" required>
  Unique topic identifier (e.g. `HX_T10346`). Must be prefixed with `HX_T`.
</ParamField>

### Response Fields

<ResponseField name="id" type="string" required>
  Unique topic identifier prefixed with `HX_T` (e.g. `HX_T10346`).
</ResponseField>

<ResponseField name="name" type="string" required>
  Topic display name (e.g. `"Machine Learning in Drug Discovery"`).
</ResponseField>

<ResponseField name="description" type="string">
  Scope description.
</ResponseField>

<ResponseField name="keywords" type="array">
  Associated keyword strings array.
</ResponseField>

<ResponseField name="subfield" type="object">
  Parent subfield.

  <Expandable title="subfield attributes">
    <ResponseField name="id" type="string">Subfield numeric ID.</ResponseField>
    <ResponseField name="name" type="string">Subfield display name.</ResponseField>
  </Expandable>
</ResponseField>

<ResponseField name="field" type="object">
  Parent field.

  <Expandable title="field attributes">
    <ResponseField name="id" type="string">Field numeric ID.</ResponseField>
    <ResponseField name="name" type="string">Field display name.</ResponseField>
  </Expandable>
</ResponseField>

<ResponseField name="domain" type="object">
  Parent domain.

  <Expandable title="domain attributes">
    <ResponseField name="id" type="string">Domain numeric ID.</ResponseField>
    <ResponseField name="name" type="string">Domain display name.</ResponseField>
  </Expandable>
</ResponseField>

<ResponseField name="siblings" type="array">
  Sibling topic clusters.

  <Expandable title="siblings attributes">
    <ResponseField name="id" type="string">Sibling topic ID (`HX_T...`).</ResponseField>
    <ResponseField name="name" type="string">Sibling topic display name.</ResponseField>
  </Expandable>
</ResponseField>

<ResponseField name="outputs_count" type="integer">
  Total number of indexed outputs in this topic.
</ResponseField>

<ResponseField name="cited_by_count" type="integer">
  Total citation count received.
</ResponseField>

<ResponseField name="ids" type="object">
  External identifiers.

  <Expandable title="ids attributes">
    <ResponseField name="wikipedia" type="string">Wikipedia URL.</ResponseField>
  </Expandable>
</ResponseField>

<ResponseField name="updated_date" type="string">
  Last updated timestamp.
</ResponseField>

<ResponseField name="created_date" type="string">
  Creation timestamp.
</ResponseField>

<RequestExample>
  ```bash cURL theme={null}
  curl -X GET "https://api.hexagraph.in/topics/HX_T10346"
  ```

  ```javascript JavaScript theme={null}
  fetch("https://api.hexagraph.in/topics/HX_T10346")
    .then(response => response.json())
    .then(data => console.log(data));
  ```

  ```python Python theme={null}
  import requests

  response = requests.get("https://api.hexagraph.in/topics/HX_T10346")
  print(response.json())
  ```

  ```go Go theme={null}
  package main

  import (
  	"fmt"
  	"io"
  	"net/http"
  )

  func main() {
  	resp, err := http.Get("https://api.hexagraph.in/topics/HX_T10346")
  	if err != nil {
  		fmt.Println("Error:", err)
  		return
  	}
  	defer resp.Body.Close()
  	body, _ := io.ReadAll(resp.Body)
  	fmt.Println(string(body))
  }
  ```
</RequestExample>

<ResponseExample>
  ```json 200 OK theme={null}
  {
    "id": "HX_T14423",
    "name": "Military Technology and Strategies",
    "description": "This cluster of papers covers various aspects related to the modernization and development of air force capabilities, including the use of unmanned aerial vehicles, radar systems, military communication, electronic components, and strategic planning. It also explores the intersection of strategic planning, foresight, and design in the context of air force modernization.",
    "keywords": [
      "Air Force",
      "Modernization",
      "Warfare",
      "Unmanned Aerial Vehicles",
      "Radar Systems",
      "Military Communication",
      "Electronic Components",
      "Strategic Planning",
      "Foresight",
      "Design"
    ],
    "ids": {
      "wikipedia": "https://en.wikipedia.org/wiki/Air_force_modernization"
    },
    "subfield": {
      "id": "2202",
      "name": "Aerospace Engineering"
    },
    "field": {
      "id": "22",
      "name": "Engineering"
    },
    "domain": {
      "id": "3",
      "name": "Physical Sciences"
    },
    "siblings": [
      {
        "id": "HX_T10069",
        "name": "Antenna Design and Analysis"
      }
    ],
    "outputs_count": 22344034,
    "cited_by_count": 843046,
    "updated_date": "2026-08-05T03:01:31",
    "created_date": "2024-01-23T15:27:22"
  }
  ```

  ```json 400 Bad Request theme={null}
  {
    "statusCode": 400,
    "message": "Only HX_ prefixed IDs are allowed",
    "error": "Bad Request"
  }
  ```

  ```json 404 Not Found theme={null}
  {
    "statusCode": 404,
    "message": "Topic with ID HX_T9999999999 not found",
    "error": "Not Found"
  }
  ```

  ```json 429 Too Many Requests theme={null}
  {
    "statusCode": 429,
    "error": "Too Many Requests",
    "message": "IP rate limit exceeded (max 30 requests per minute). Please try again in 42 seconds (at 11:40:32 UTC).",
    "reset_in_seconds": 42,
    "reset_at_utc": "2026-08-05T11:40:32.000Z"
  }
  ```
</ResponseExample>