United States National Library of Medicine Search API

openapi: 3.0.3
info:
  title: NCBI URL BLAST Search API
  description: 'The NCBI BLAST URL API allows developers to submit BLAST (Basic Local Alignment Search Tool) sequence searches for processing at NCBI using HTTPS. The API operates in three phases: (1) PUT request to submit a search and receive a request ID (RID), (2) polling GET requests to check search status, (3) GET request to retrieve results in the desired format. Supports nucleotide (blastn, blastx) and protein (blastp, tblastn, tblastx) searches.'
  version: 1.0.0
  contact:
    name: NCBI BLAST
    url: https://blast.ncbi.nlm.nih.gov/doc/blast-help/developerinfo.html
  license:
    name: Public Domain
    url: https://www.usa.gov/government-works
servers:
- url: https://blast.ncbi.nlm.nih.gov/blast
  description: NCBI BLAST Server
tags:
- name: Search
  description: Search Entrez databases
paths:
  /esearch.fcgi:
    get:
      operationId: searchDatabase
      summary: Search Entrez Database
      description: Search any Entrez database and retrieve document identifiers (UIDs) matching a query. Supports full Entrez query syntax including Boolean operators, field tags, and date ranges.
      tags:
      - Search
      parameters:
      - name: db
        in: query
        description: Target Entrez database (e.g. pubmed, nuccore, protein, gene, snp, mesh, pmc)
        required: true
        schema:
          type: string
        example: pubmed
      - name: term
        in: query
        description: Entrez text query with optional field tags and Boolean operators
        required: true
        schema:
          type: string
        example: cancer[Title] AND 2023[PDAT]
      - name: api_key
        in: query
        description: NCBI API key for increased rate limits
        required: false
        schema:
          type: string
      - name: retmax
        in: query
        description: Maximum number of UIDs to return (default 20, max 10000)
        required: false
        schema:
          type: integer
          default: 20
          maximum: 10000
      - name: retstart
        in: query
        description: Index of first UID in results (for pagination)
        required: false
        schema:
          type: integer
          default: 0
      - name: retmode
        in: query
        description: Output format
        required: false
        schema:
          type: string
          enum:
          - json
          - xml
          default: json
      - name: sort
        in: query
        description: Sort order for results
        required: false
        schema:
          type: string
          enum:
          - relevance
          - pub+date
          - Author
          - JournalName
      - name: datetype
        in: query
        description: Date type for date range filtering
        required: false
        schema:
          type: string
          enum:
          - PDAT
          - MDAT
          - EDAT
      - name: mindate
        in: query
        description: Minimum date for range filter (YYYY/MM/DD)
        required: false
        schema:
          type: string
        example: 2023/01/01
      - name: maxdate
        in: query
        description: Maximum date for range filter (YYYY/MM/DD)
        required: false
        schema:
          type: string
        example: 2023/12/31
      - name: usehistory
        in: query
        description: Store results on NCBI server (y/n)
        required: false
        schema:
          type: string
          enum:
          - y
          - n
      responses:
        '200':
          description: Search results with UIDs and counts
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ESearchResult'
  /espell.fcgi:
    get:
      operationId: checkSpelling
      summary: Check Query Spelling
      description: Retrieve spelling suggestions for a search term in a given Entrez database. Helpful for correcting misspelled gene names, species names, or medical terms.
      tags:
      - Search
      parameters:
      - name: db
        in: query
        description: Target Entrez database
        required: true
        schema:
          type: string
        example: pubmed
      - name: term
        in: query
        description: Query term to check spelling for
        required: true
        schema:
          type: string
        example: asthmaa
      - name: api_key
        in: query
        required: false
        schema:
          type: string
      responses:
        '200':
          description: Spelling suggestions
          content:
            text/xml:
              schema:
                type: string
components:
  schemas:
    ESearchResult:
      type: object
      description: Results from an Entrez search query
      properties:
        esearchresult:
          type: object
          properties:
            count:
              type: string
              description: Total number of matching records
            retmax:
              type: string
              description: Number of UIDs returned
            retstart:
              type: string
              description: Index of first UID returned
            querykey:
              type: string
              description: Server-side query key (if usehistory=y)
            webenv:
              type: string
              description: Web environment token (if usehistory=y)
            idlist:
              type: array
              description: List of returned UIDs
              items:
                type: string
            translationset:
              type: array
              description: Query translations applied
              items:
                type: object
            querytranslation:
              type: string
              description: Translated query as used by Entrez