openapi: 3.1.0
info:
  title: KEGG REST API
  description: >
    The Kyoto Encyclopedia of Genes and Genomes (KEGG) REST API provides
    programmatic access to KEGG databases covering biological pathways,
    metabolic networks, molecular interactions, drug targets, disease
    associations, chemical compounds, genomic sequences, and functional
    orthologs across thousands of organisms. The API exposes seven core
    operations — info, list, find, get, conv, link, and ddi — enabling
    identifier conversion, cross-database linking, keyword and structure
    searches, and full entry retrieval in text, KGML, and JSON formats.
    Academic use is free; commercial use requires a license from Pathway
    Solutions. Rate limit is 3 requests per second per client.
  version: "1.0.0"
  contact:
    name: KEGG Support
    url: https://www.kegg.jp/kegg/feedback.html
  termsOfService: https://www.kegg.jp/kegg/legal.html
  license:
    name: Academic Use Only
    url: https://www.kegg.jp/kegg/legal.html
externalDocs:
  description: KEGG API Documentation
  url: https://www.kegg.jp/kegg/rest/keggapi.html
servers:
  - url: https://rest.kegg.jp
    description: KEGG REST API server
tags:
  - name: info
    description: Display database release information and statistics
  - name: list
    description: Obtain a list of entry identifiers and associated names
  - name: find
    description: Search entries by keyword or molecular property
  - name: get
    description: Retrieve specific database entries
  - name: conv
    description: Convert identifiers between KEGG and external databases
  - name: link
    description: Find related entries using database cross-references
  - name: ddi
    description: Find adverse drug-drug interactions
paths:
  /info/{database}:
    get:
      operationId: getInfo
      summary: Get database information
      description: >
        Display release information and statistics for a KEGG database,
        including the number of entries and linked databases.
      tags:
        - info
      parameters:
        - name: database
          in: path
          required: true
          description: >
            KEGG database name. Valid values include: kegg, pathway, brite,
            module, ko, genes, genome, ligand, compound, glycan, reaction,
            rclass, enzyme, network, variant, disease, drug, dgroup, and
            any organism code (e.g., hsa, eco).
          schema:
            type: string
            enum:
              - kegg
              - pathway
              - brite
              - module
              - ko
              - genes
              - genome
              - ligand
              - compound
              - glycan
              - reaction
              - rclass
              - enzyme
              - network
              - variant
              - disease
              - drug
              - dgroup
      responses:
        "200":
          description: Database release information and statistics
          content:
            text/plain:
              schema:
                type: string
              example: |
                pathway          Release 113.0+/09-25, Sep 24
                                 Kanehisa Laboratories
                KEGG PATHWAY Database
                # of pathways:   572
                # of genes:      8,022 (hsa)
        "400":
          description: Bad request — invalid database name or syntax error
        "404":
          description: Not found — database does not exist
  /list/{database}:
    get:
      operationId: listDatabase
      summary: List entry identifiers for a database
      description: >
        Obtain a list of entry identifiers and associated names for a KEGG
        database. Returns tab-delimited text.
      tags:
        - list
      parameters:
        - name: database
          in: path
          required: true
          description: >
            KEGG database name or organism code. Supported databases: pathway,
            brite, module, ko, genome, compound, glycan, reaction, rclass,
            enzyme, disease, drug, dgroup, network, variant, and organism codes.
          schema:
            type: string
      responses:
        "200":
          description: Tab-delimited list of entry identifiers and names
          content:
            text/plain:
              schema:
                type: string
              example: |
                path:hsa00010	Glycolysis / Gluconeogenesis - Homo sapiens (human)
                path:hsa00020	Citrate cycle (TCA cycle) - Homo sapiens (human)
        "400":
          description: Bad request — invalid database or syntax error
        "404":
          description: Not found
  /list/pathway/{org}:
    get:
      operationId: listPathwaysByOrganism
      summary: List pathways for a specific organism
      description: >
        Obtain a list of pathway entry identifiers and names for a specific
        organism identified by its KEGG organism code (e.g., hsa for human,
        eco for E. coli).
      tags:
        - list
      parameters:
        - name: org
          in: path
          required: true
          description: KEGG organism code (e.g., hsa, eco, mmu)
          schema:
            type: string
            example: hsa
      responses:
        "200":
          description: Tab-delimited list of pathway identifiers and names for the organism
          content:
            text/plain:
              schema:
                type: string
        "400":
          description: Bad request
        "404":
          description: Not found
  /find/{database}/{query}:
    get:
      operationId: findEntries
      summary: Search entries by keyword
      description: >
        Search entries in a KEGG database by keyword or query data. Returns
        tab-delimited text with matching entry identifiers and names.
        Searchable fields vary by database and may include ENTRY, NAME,
        SYMBOL, COMPOSITION, and DEFINITION.
      tags:
        - find
      parameters:
        - name: database
          in: path
          required: true
          description: >
            KEGG database to search. Supported: genes, ligand, compound,
            glycan, reaction, rclass, enzyme, disease, drug, dgroup, environ,
            network, variant, ko, genome, pathway, brite, module.
          schema:
            type: string
        - name: query
          in: path
          required: true
          description: Keyword(s) to search for, URL-encoded
          schema:
            type: string
            example: shikimate+pathway
      responses:
        "200":
          description: Tab-delimited list of matching entries
          content:
            text/plain:
              schema:
                type: string
              example: |
                cpd:C00493	shikimate
                cpd:C02637	3-Dehydroshikimate
        "400":
          description: Bad request
        "404":
          description: Not found
  /find/{database}/{query}/{option}:
    get:
      operationId: findEntriesWithOption
      summary: Search compound or drug entries by molecular property
      description: >
        Search compound or drug database entries by molecular formula, exact
        mass, or molecular weight. The option parameter specifies the search
        type. Only applicable to compound and drug databases.
      tags:
        - find
      parameters:
        - name: database
          in: path
          required: true
          description: Database to search — compound or drug
          schema:
            type: string
            enum:
              - compound
              - drug
        - name: query
          in: path
          required: true
          description: >
            Molecular formula (e.g., C6H12O6), exact mass range (e.g.,
            174.05-174.15), or molecular weight range (e.g., 180-180)
          schema:
            type: string
        - name: option
          in: path
          required: true
          description: Search type
          schema:
            type: string
            enum:
              - formula
              - exact_mass
              - mol_weight
              - nop
      responses:
        "200":
          description: Tab-delimited list of matching entries
          content:
            text/plain:
              schema:
                type: string
        "400":
          description: Bad request
        "404":
          description: Not found
  /get/{dbentries}:
    get:
      operationId: getEntries
      summary: Retrieve database entries
      description: >
        Retrieve one or more KEGG database entries in their default flat-file
        format. Up to 10 entries can be retrieved in a single request by
        separating identifiers with plus signs (e.g., hsa:10458+ece:Z5100).
      tags:
        - get
      parameters:
        - name: dbentries
          in: path
          required: true
          description: >
            One or more KEGG entry identifiers, separated by plus signs.
            Maximum 10 entries per request. Format: database:id (e.g.,
            hsa:10458, cpd:C01290, path:hsa00010).
          schema:
            type: string
            example: hsa:10458+ece:Z5100
      responses:
        "200":
          description: KEGG flat-file format entry data
          content:
            text/plain:
              schema:
                type: string
        "400":
          description: Bad request
        "404":
          description: Not found
  /get/{dbentries}/{option}:
    get:
      operationId: getEntriesWithOption
      summary: Retrieve database entries in a specific format
      description: >
        Retrieve one or more KEGG database entries in a specified output
        format. Options include amino acid sequences, nucleotide sequences,
        molecular structure files, pathway images, KGML XML, and JSON.
      tags:
        - get
      parameters:
        - name: dbentries
          in: path
          required: true
          description: >
            One or more KEGG entry identifiers separated by plus signs.
            Maximum 10 entries per request.
          schema:
            type: string
        - name: option
          in: path
          required: true
          description: Output format option
          schema:
            type: string
            enum:
              - aaseq
              - ntseq
              - mol
              - kcf
              - image
              - image2x
              - conf
              - kgml
              - json
      responses:
        "200":
          description: Entry data in the requested format
          content:
            text/plain:
              schema:
                type: string
            application/xml:
              schema:
                type: string
            application/json:
              schema:
                type: object
            image/gif:
              schema:
                type: string
                format: binary
            image/png:
              schema:
                type: string
                format: binary
        "400":
          description: Bad request
        "404":
          description: Not found
  /conv/{target_db}/{source_db}:
    get:
      operationId: convertIdentifiers
      summary: Convert identifiers between databases
      description: >
        Convert identifiers between KEGG and external databases. Returns a
        tab-delimited mapping of source to target identifiers. Supports
        conversion between KEGG gene identifiers and NCBI Gene IDs, NCBI
        Protein IDs, and UniProt accessions, as well as between KEGG
        compound IDs and PubChem CIDs and ChEBI IDs.
      tags:
        - conv
      parameters:
        - name: target_db
          in: path
          required: true
          description: >
            Target database for conversion. For genes: ncbi-geneid,
            ncbi-proteinid, uniprot, or a KEGG organism code. For chemicals:
            pubchem, chebi, or compound.
          schema:
            type: string
            example: ncbi-geneid
        - name: source_db
          in: path
          required: true
          description: >
            Source database or organism code. For genes: ncbi-geneid,
            ncbi-proteinid, uniprot, or a KEGG organism code. For chemicals:
            pubchem, chebi, or compound.
          schema:
            type: string
            example: hsa
      responses:
        "200":
          description: Tab-delimited identifier mapping
          content:
            text/plain:
              schema:
                type: string
              example: |
                ncbi-geneid:10458	hsa:10458
                ncbi-geneid:1131	hsa:1131
        "400":
          description: Bad request
        "404":
          description: Not found
  /conv/{target_db}/{dbentries}:
    get:
      operationId: convertEntryIdentifiers
      summary: Convert specific entry identifiers
      description: >
        Convert specific KEGG entry identifiers to their equivalents in an
        external database, or convert external database identifiers to KEGG
        identifiers. Up to 10 entries per request.
      tags:
        - conv
      parameters:
        - name: target_db
          in: path
          required: true
          description: >
            Target database for conversion (e.g., ncbi-geneid, uniprot,
            pubchem, chebi, or a KEGG organism code).
          schema:
            type: string
        - name: dbentries
          in: path
          required: true
          description: >
            One or more entry identifiers separated by plus signs.
            Maximum 10 entries per request.
          schema:
            type: string
            example: ncbi-geneid:10458+ncbi-geneid:1131
      responses:
        "200":
          description: Tab-delimited identifier mapping
          content:
            text/plain:
              schema:
                type: string
        "400":
          description: Bad request
        "404":
          description: Not found
  /link/{target_db}/{source_db}:
    get:
      operationId: linkDatabases
      summary: Find cross-references between databases
      description: >
        Find related entries between two KEGG databases using cross-references.
        Returns tab-delimited text listing relationships between entries in the
        source and target databases.
      tags:
        - link
      parameters:
        - name: target_db
          in: path
          required: true
          description: >
            Target KEGG database. Supported: pathway, brite, module, ko,
            genes, genome, compound, glycan, reaction, rclass, enzyme,
            disease, drug, dgroup, network, variant, and organism codes.
          schema:
            type: string
            example: pathway
        - name: source_db
          in: path
          required: true
          description: >
            Source KEGG database or organism code.
          schema:
            type: string
            example: hsa
      responses:
        "200":
          description: Tab-delimited cross-reference relationships
          content:
            text/plain:
              schema:
                type: string
              example: |
                hsa:10458	path:hsa04010
                hsa:10458	path:hsa04012
        "400":
          description: Bad request
        "404":
          description: Not found
  /link/{target_db}/{dbentries}:
    get:
      operationId: linkEntries
      summary: Find cross-references for specific entries
      description: >
        Find related entries in a target KEGG database for specific source
        entries. Returns tab-delimited cross-reference relationships.
        Up to 10 entries per request. RDF output formats (turtle, n-triple)
        are also supported via the option parameter.
      tags:
        - link
      parameters:
        - name: target_db
          in: path
          required: true
          description: Target KEGG database
          schema:
            type: string
        - name: dbentries
          in: path
          required: true
          description: >
            One or more source entry identifiers separated by plus signs.
            Maximum 10 entries per request.
          schema:
            type: string
            example: cpd:C00031+cpd:C00033
      responses:
        "200":
          description: Tab-delimited cross-reference relationships
          content:
            text/plain:
              schema:
                type: string
        "400":
          description: Bad request
        "404":
          description: Not found
  /ddi/{dbentry}:
    get:
      operationId: getDrugInteraction
      summary: Get adverse drug-drug interactions for a single drug
      description: >
        Find adverse drug-drug interactions for a single drug entry. Returns
        tab-delimited text listing interacting drug pairs and severity data.
        Drug entries can be specified using KEGG drug IDs (D prefix), NDC
        codes, or YJ codes.
      tags:
        - ddi
      parameters:
        - name: dbentry
          in: path
          required: true
          description: >
            A single KEGG drug identifier. Formats: KEGG drug ID (e.g.,
            D00001), NDC code, or YJ code.
          schema:
            type: string
            example: D00001
      responses:
        "200":
          description: Tab-delimited drug-drug interaction data
          content:
            text/plain:
              schema:
                type: string
              example: |
                D00001	D00002	CI
                D00001	D00005	precaution
        "400":
          description: Bad request
        "404":
          description: Not found
  /ddi/{dbentries}:
    get:
      operationId: getDrugInteractions
      summary: Get adverse drug-drug interactions for multiple drugs
      description: >
        Find adverse drug-drug interactions among multiple drug entries.
        Returns tab-delimited text listing interacting drug pairs and their
        interaction severity. Drug entries can be specified using KEGG drug
        IDs, NDC codes, or YJ codes, separated by plus signs.
      tags:
        - ddi
      parameters:
        - name: dbentries
          in: path
          required: true
          description: >
            Multiple KEGG drug identifiers separated by plus signs (e.g.,
            D00001+D00002+D00003).
          schema:
            type: string
            example: D00001+D00002
      responses:
        "200":
          description: Tab-delimited drug-drug interaction data
          content:
            text/plain:
              schema:
                type: string
        "400":
          description: Bad request
        "404":
          description: Not found