ConceptNet Similarity API

openapi: 3.0.3
info:
  title: ConceptNet REST Concepts Similarity API
  description: ConceptNet is a freely available multilingual knowledge graph providing computers access to common-sense knowledge. The REST API exposes the full ConceptNet 5 knowledge graph via JSON-LD endpoints. Consumers can look up concept nodes by language and term, query edges by relation type, retrieve semantically related terms ranked by Numberbatch embedding similarity, compute pairwise relatedness scores between concepts, and normalize natural-language text into canonical ConceptNet URIs. No authentication or API key is required.
  version: '5.7'
  license:
    name: CC BY-SA 4.0
    url: https://creativecommons.org/licenses/by-sa/4.0/
  contact:
    name: ConceptNet Users Group
    url: https://groups.google.com/g/conceptnet-users
  x-website: https://conceptnet.io
  x-github: https://github.com/commonsense/conceptnet5
servers:
- url: https://api.conceptnet.io
  description: ConceptNet public API
tags:
- name: Similarity
  description: Semantic similarity and relatedness using Numberbatch embeddings
paths:
  /related/{uri}:
    get:
      operationId: getRelatedConcepts
      summary: Find semantically related concepts
      description: Returns a ranked list of concepts most semantically related to the given URI, using ConceptNet Numberbatch word vector similarity. Results are sorted by descending relatedness weight. This endpoint and /relatedness each count as 2 requests against the rate limit quota (3,600 req/hour, 120 req/min). The optional filter parameter restricts results to a particular language subtree.
      tags:
      - Similarity
      parameters:
      - name: uri
        in: path
        description: ConceptNet URI path (e.g. c/en/dog — the leading slash is part of the base path, so omit it here)
        required: true
        schema:
          type: string
          example: c/en/dog
      - name: limit
        in: query
        description: Maximum number of related concepts to return (0-100)
        required: false
        schema:
          type: integer
          minimum: 0
          maximum: 100
          default: 50
      - name: filter
        in: query
        description: Restrict results to URIs under this prefix (e.g. /c/en to limit to English concepts)
        required: false
        schema:
          type: string
          example: /c/en
      responses:
        '200':
          description: Ranked list of related concepts with weights
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/RelatedList'
              example:
                '@id': /related/c/en/dog
                related:
                - '@id': /c/en/puppy
                  weight: 0.713
                - '@id': /c/en/canine
                  weight: 0.698
                - '@id': /c/en/pet
                  weight: 0.621
        '404':
          description: URI not found in embedding space
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
  /relatedness:
    get:
      operationId: getRelatedness
      summary: Compute pairwise relatedness score
      description: Returns a single floating-point relatedness score between 0 and 1 for any two ConceptNet concept URIs, computed from Numberbatch word vector cosine similarity. A score of 1.0 indicates maximum similarity and 0.0 indicates no detectable relationship. This endpoint and /related each count as 2 requests against the rate limit quota.
      tags:
      - Similarity
      parameters:
      - name: node1
        in: query
        description: First ConceptNet concept URI
        required: true
        schema:
          type: string
          example: /c/en/dog
      - name: node2
        in: query
        description: Second ConceptNet concept URI
        required: true
        schema:
          type: string
          example: /c/en/cat
      responses:
        '200':
          description: Relatedness result
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/RelatednessResult'
              example:
                '@id': /relatedness?node1=/c/en/dog&node2=/c/en/cat
                value: 0.849
                node1:
                  '@id': /c/en/dog
                node2:
                  '@id': /c/en/cat
        '400':
          description: Missing or invalid node parameters
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
components:
  schemas:
    RelatednessResult:
      type: object
      description: Pairwise semantic relatedness result
      properties:
        '@id':
          type: string
          description: URI of this relatedness result
        value:
          type: number
          format: float
          description: Relatedness score between 0.0 and 1.0
          example: 0.849
        node1:
          $ref: '#/components/schemas/ConceptRef'
        node2:
          $ref: '#/components/schemas/ConceptRef'
    WeightedConcept:
      type: object
      description: A concept with a numeric relatedness weight
      properties:
        '@id':
          type: string
          description: ConceptNet URI of the related concept
          example: /c/en/puppy
        weight:
          type: number
          format: float
          description: Relatedness score (0.0-1.0)
          example: 0.713
    RelatedList:
      type: object
      description: Ranked list of semantically related concepts
      properties:
        '@id':
          type: string
          description: URI of this related-terms result
          example: /related/c/en/dog
        related:
          type: array
          items:
            $ref: '#/components/schemas/WeightedConcept'
    Error:
      type: object
      description: API error response
      properties:
        error:
          type: string
          description: Error type identifier
        details:
          type: string
          description: Human-readable error description
    ConceptRef:
      type: object
      description: Reference to a ConceptNet concept node
      properties:
        '@id':
          type: string
          description: ConceptNet URI
          example: /c/en/dog
        label:
          type: string
          description: Human-readable label
          example: dog
        language:
          type: string
          description: BCP-47 language code
          example: en
        term:
          type: string
          description: Concept URI (same as @id)
          example: /c/en/dog
        sense_label:
          type: string
          description: Part-of-speech or sense label if applicable
          example: n