ARD Registry API

openapi: 3.1.0
info:
  title: Agentic Resource Discovery Registry API
  version: 0.5.0
  description: |
    Universal federated discovery API specification for AI agents, tools, and capabilities.
    Allows LLM orchestrators to semantically search and discover registries for relevant capabilities
    and enables registry-to-registry federated query routing.
paths:
  /search:
    post:
      summary: Semantic Search Registry
      description: |
        Query a registry with natural language to find matching capabilities.
        Accepts a shared semantic and structural query object. Supports multi-hop federation.
      operationId: searchAgents
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/SearchRequest'
      responses:
        '200':
          description: Successful search operation.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/SearchResponse'
        '400':
          $ref: '#/components/responses/400BadRequest'
        '401':
          $ref: '#/components/responses/401Unauthorized'
        '429':
          $ref: '#/components/responses/429TooManyRequests'
        '500':
          $ref: '#/components/responses/500InternalError'

  /explore:
    post:
      summary: Dynamic Registry Introspection
      description: |
        Aggregates statistical facets and bucketing over the matched search space. 
        Returns counts instead of ranked catalog entries. 
      operationId: exploreRegistry
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ExploreRequest'
      responses:
        '200':
          description: Successful explore operation.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ExploreResponse'
        '400':
          $ref: '#/components/responses/400BadRequest'
        '401':
          $ref: '#/components/responses/401Unauthorized'
        '429':
          $ref: '#/components/responses/429TooManyRequests'
        '501':
          description: Dynamic registry exploration is not implemented by this server.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
        '500':
          $ref: '#/components/responses/500InternalError'

  /agents:
    get:
      summary: Browse Catalog Entries
      description: |
        Deterministic, highly cacheable listing endpoint designed for developer portals.
        Relies on strict EBNF database filtering instead of natural language search.
      operationId: listAgents
      parameters:
        - name: filter
          in: query
          required: false
          description: EBNF-like filter expression (e.g., "type = 'application/mcp-server-card+json' AND createdAfter > '2026-01-01'")
          schema:
            type: string
        - name: orderBy
          in: query
          required: false
          description: Field and sorting direction (e.g., "displayName", "updatedAt DESC")
          schema:
            type: string
        - name: pageSize
          in: query
          required: false
          description: Maximum number of entries to return.
          schema:
            type: integer
            default: 20
            maximum: 100
        - name: pageToken
          in: query
          required: false
          description: Token for pagination.
          schema:
            type: string
      responses:
        '200':
          description: Successful deterministic list operation.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ListResponse'
        '400':
          $ref: '#/components/responses/400BadRequest'
        '401':
          $ref: '#/components/responses/401Unauthorized'
        '429':
          $ref: '#/components/responses/429TooManyRequests'
        '500':
          $ref: '#/components/responses/500InternalError'

components:
  schemas:
    QueryModel:
      type: object
      properties:
        text:
          type: string
          description: Natural language description narrows the set by semantic relevance.
          example: "find me a weather lookup tool"
        filter:
          type: object
          description: |
            Structured constraints. Keys are field paths (can be dot-separated for nested fields). 
            Values are arrays or scalar values.
          additionalProperties:
            oneOf:
              - type: string
              - type: array
                items:
                  type: string
          example:
            type: ["application/mcp-server-card+json"]
            "trustManifest.attestations.type": ["SOC2-Type2"]
      additionalProperties: false

    SearchQueryModel:
      allOf:
        - $ref: '#/components/schemas/QueryModel'
        - type: object
          required:
            - text

    SearchRequest:
      type: object
      required:
        - query
      properties:
        query:
          $ref: '#/components/schemas/SearchQueryModel'
        federation:
          type: string
          enum: [auto, referrals, none]
          default: auto
        pageSize:
          type: integer
          default: 10
          description: Maximum number of search results to return.
        pageToken:
          type: string
          description: Pagination token.
      additionalProperties: false

    ExploreRequest:
      type: object
      required:
        - resultType
      properties:
        query:
          $ref: '#/components/schemas/QueryModel'
        resultType:
          type: object
          required:
            - facets
          properties:
            facets:
              type: array
              items:
                $ref: '#/components/schemas/ExploreFacetRequest'
      additionalProperties: false

    ExploreFacetRequest:
      type: object
      required:
        - field
      properties:
        field:
          type: string
          description: Dot-separated path of the catalogEntry property to aggregate.
          example: "type"
        limit:
          type: integer
          default: 20
        minCount:
          type: integer
          default: 1
      additionalProperties: false

    ExploreResponse:
      type: object
      required:
        - resultType
        - facets
      properties:
        resultType:
          type: string
          enum: [facets]
        facets:
          type: object
          additionalProperties:
            $ref: '#/components/schemas/ExploreFacetResult'
      additionalProperties: false

    ExploreFacetResult:
      type: object
      required:
        - buckets
      properties:
        buckets:
          type: array
          items:
            $ref: '#/components/schemas/ExploreFacetBucket'
        otherCount:
          type: integer
      additionalProperties: false

    ExploreFacetBucket:
      type: object
      required:
        - value
        - count
      properties:
        value:
          type: string
        count:
          type: integer
      additionalProperties: false

    SearchResponse:
      type: object
      required:
        - results
      properties:
        results:
          type: array
          items:
            $ref: '#/components/schemas/SearchResultItem'
        referrals:
          type: array
          description: List of upstream registries recommended to the client. Only returned in 'referrals' federation mode.
          items:
            $ref: '#/components/schemas/RegistryReferral'
        pageToken:
          type: string
          description: Token for paging subsequent results.
      additionalProperties: false

    SearchResultItem:
      allOf:
        - $ref: './ai-catalog.schema.json#/$defs/catalogEntry'
      type: object
      required:
        - score
        - source
      properties:
        score:
          type: integer
          minimum: 0
          maximum: 100
          description: "Semantic relevance rating (0 to 100) computed by the registry. Note: This is not a security or trust score."
          example: 95
        source:
          type: string
          format: uri
          description: The URL endpoint of the registry where this entry was indexed.
          example: "https://registry.acme.com/api/v1/"

    RegistryReferral:
      type: object
      required:
        - identifier
        - displayName
        - type
        - url
      properties:
        identifier:
          type: string
          description: Logical identifier of the referred registry.
          example: "urn:air:nlweb.ai:registry:public"
        displayName:
          type: string
          description: Name of the referred registry.
          example: "Public Agent Finder"
        type:
          type: string
          enum: [application/ai-registry, application/ai-registry+json]
          description: Registry media type identifier.
        url:
          type: string
          format: uri
          description: Endpoint URL for the referred registry's search route.
          example: "https://finder.nlweb.ai/search"

    ListResponse:
      type: object
      required:
        - items
      properties:
        items:
          type: array
          items:
            $ref: './ai-catalog.schema.json#/$defs/catalogEntry'
        total:
          type: integer
          description: Total count of matching entries in the registry.
        pageToken:
          type: string
          description: Token for paginating subsequent results.

    Error:
      type: object
      required:
        - errorCode
        - message
      properties:
        errorCode:
          type: string
          description: Standard uppercase error classification code.
          example: "INVALID_ARGUMENT"
        message:
          type: string
          description: Human-readable description explaining the error.
          example: "The filter expression syntax 'type = MCP' is invalid. Did you mean 'type = application/mcp-server-card+json'?"

  responses:
    400BadRequest:
      description: Malformed request payload or invalid syntax.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    401Unauthorized:
      description: Credentials missing or rejected.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    429TooManyRequests:
      description: Rate limit exceeded.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
    500InternalError:
      description: Internal server error.
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'