openapi: 3.1.0
info:
  title: NCBI Entrez E-utilities History Info API
  description: The Entrez Programming Utilities (E-utilities) provide a stable interface to the NCBI Entrez query and database system. Nine server-side programs allow searching, fetching, posting, linking, and summarizing records across PubMed and 38 NCBI databases including PubMed Central, Gene, Nuccore, and Protein. Supports searching 35M+ biomedical citations, retrieving abstracts, full-text links, MeSH terms, and related article metadata.
  version: v1.0.0
  termsOfService: https://www.ncbi.nlm.nih.gov/home/about/policies.shtml
  contact:
    name: NCBI Help Desk
    url: https://support.nlm.nih.gov/
    email: info@ncbi.nlm.nih.gov
  license:
    name: NCBI Data Use Policies
    url: https://www.ncbi.nlm.nih.gov/home/about/policies.shtml
servers:
- url: https://eutils.ncbi.nlm.nih.gov/entrez/eutils
  description: NCBI E-utilities production server
tags:
- name: Info
  description: Operations for retrieving database metadata and information
paths:
  /einfo.fcgi:
    get:
      summary: EInfo - Get database information
      description: Provides a list of all valid Entrez databases, or information about a single database including field names, index terms, links to other Entrez databases, and other metadata.
      operationId: EInfo
      tags:
      - Info
      parameters:
      - name: db
        in: query
        description: Target database. Omit to return a list of all valid Entrez databases.
        required: false
        schema:
          type: string
          example: pubmed
      - name: version
        in: query
        description: Set to '2.0' for EInfo XML version 2.0 with additional field attributes.
        required: false
        schema:
          type: string
          enum:
          - '2.0'
      - name: retmode
        in: query
        description: 'Response format. Values: xml (default), json.'
        required: false
        schema:
          type: string
          enum:
          - xml
          - json
          default: xml
      - name: tool
        in: query
        description: Name of application making the call.
        required: false
        schema:
          type: string
      - name: email
        in: query
        description: Contact email address.
        required: false
        schema:
          type: string
          format: email
      - name: api_key
        in: query
        description: API key to enable higher request rate.
        required: false
        schema:
          type: string
      responses:
        '200':
          description: Database information or list of databases
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/EInfoResult'
            application/xml:
              schema:
                $ref: '#/components/schemas/EInfoResult'
components:
  schemas:
    EInfoResult:
      type: object
      properties:
        einforesult:
          type: object
          properties:
            dblist:
              type: array
              items:
                type: string
              description: List of all valid Entrez databases (when no db parameter).
            dbinfo:
              type: object
              description: Detailed database information when db parameter is supplied.
              properties:
                dbname:
                  type: string
                menuname:
                  type: string
                description:
                  type: string
                dbbuild:
                  type: string
                count:
                  type: string
                lastupdate:
                  type: string
                fieldlist:
                  type: array
                  items:
                    type: object
                    properties:
                      name:
                        type: string
                      fullname:
                        type: string
                      description:
                        type: string
                      termcount:
                        type: string
                      isdate:
                        type: string
                      isnumerical:
                        type: string
                      singletoken:
                        type: string
                      hierarchy:
                        type: string
                      ishidden:
                        type: string
                linklist:
                  type: array
                  items:
                    type: object
                    properties:
                      name:
                        type: string
                      menu:
                        type: string
                      description:
                        type: string
                      dbto:
                        type: string
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      in: query
      name: api_key
      description: 'Optional NCBI API key. Without a key: 3 requests/second. With a key: 10 requests/second. Register at https://www.ncbi.nlm.nih.gov/account/'