ExchangeRate-API Pair Conversion API

openapi: 3.2.0
info:
  title: ExchangeRate Enriched Data Pair Conversion API
  description: ExchangeRate-API is a currency exchange rate API providing authoritative daily and intraday foreign exchange rates for 161 currencies. The v6 API surface includes Standard (Latest) rates, Pair conversion, Enriched data (locale, symbol, flag), Historical rates back to 1990, Supported codes, and an API request Quota endpoint. A separate no-key Open Access endpoint (open.er-api.com) provides once-daily rates with attribution.
  version: 6.0.0
  termsOfService: https://www.exchangerate-api.com/terms
  contact:
    name: ExchangeRate-API Support
    url: https://www.exchangerate-api.com/contact
    email: contact@exchangerate-api.com
  license:
    name: Proprietary
    url: https://www.exchangerate-api.com/terms
servers:
- url: https://v6.exchangerate-api.com/v6
  description: ExchangeRate-API v6 Production (API key required)
- url: https://open.er-api.com/v6
  description: ExchangeRate-API Open Access (no API key, attribution required)
security:
- apiKeyPath: []
tags:
- name: Pair Conversion
  description: Direct currency-to-currency exchange rate and optional amount conversion.
paths:
  /{api_key}/pair/{base_code}/{target_code}:
    get:
      tags:
      - Pair Conversion
      summary: Get Pair Conversion Rate
      description: Returns the exchange rate between a base and a target currency.
      operationId: getPairConversion
      parameters:
      - $ref: '#/components/parameters/ApiKey'
      - $ref: '#/components/parameters/BaseCode'
      - $ref: '#/components/parameters/TargetCode'
      responses:
        '200':
          description: Successful response with conversion rate for the currency pair.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/PairResponse'
        '400':
          description: Error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
  /{api_key}/pair/{base_code}/{target_code}/{amount}:
    get:
      tags:
      - Pair Conversion
      summary: Get Pair Conversion With Amount
      description: Returns the exchange rate between a base and a target currency along with the converted amount.
      operationId: getPairConversionWithAmount
      parameters:
      - $ref: '#/components/parameters/ApiKey'
      - $ref: '#/components/parameters/BaseCode'
      - $ref: '#/components/parameters/TargetCode'
      - $ref: '#/components/parameters/Amount'
      responses:
        '200':
          description: Successful response with conversion rate and converted amount.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/PairAmountResponse'
        '400':
          description: Error response.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
components:
  parameters:
    ApiKey:
      name: api_key
      in: path
      required: true
      description: Your ExchangeRate-API dashboard API key.
      schema:
        type: string
    Amount:
      name: amount
      in: path
      required: true
      description: Decimal amount to convert (xxxx.xxxx format).
      schema:
        type: number
        format: double
        example: 100.0
    BaseCode:
      name: base_code
      in: path
      required: true
      description: ISO 4217 three-letter currency code for the base currency (e.g. USD).
      schema:
        type: string
        pattern: ^[A-Z]{3}$
        example: USD
    TargetCode:
      name: target_code
      in: path
      required: true
      description: ISO 4217 three-letter currency code for the target currency (e.g. EUR).
      schema:
        type: string
        pattern: ^[A-Z]{3}$
        example: EUR
  schemas:
    ErrorResponse:
      type: object
      description: Standard error envelope returned when a request cannot be fulfilled.
      properties:
        result:
          type: string
          description: Status indicator (error).
          example: error
        error-type:
          type: string
          description: Machine-readable error code.
          enum:
          - unsupported-code
          - malformed-request
          - invalid-key
          - inactive-account
          - quota-reached
          - plan-upgrade-required
          - no-data-available
    PairResponse:
      type: object
      description: Pair conversion response without amount.
      properties:
        result:
          type: string
          description: Status indicator.
        documentation:
          type: string
          format: uri
          description: Link to the API documentation.
        terms_of_use:
          type: string
          format: uri
          description: Link to the terms of use.
        time_last_update_unix:
          type: integer
          description: Last update Unix timestamp.
        time_last_update_utc:
          type: string
          description: Last update in UTC.
        time_next_update_unix:
          type: integer
          description: Next update Unix timestamp.
        time_next_update_utc:
          type: string
          description: Next update in UTC.
        base_code:
          type: string
          description: Supplied base currency.
        target_code:
          type: string
          description: Supplied target currency.
        conversion_rate:
          type: number
          description: Exchange rate between base and target.
    PairAmountResponse:
      allOf:
      - $ref: '#/components/schemas/PairResponse'
      - type: object
        description: Pair conversion with additional converted amount.
        properties:
          conversion_result:
            type: number
            description: Result of converting the requested amount at the current rate.
  securitySchemes:
    apiKeyPath:
      type: apiKey
      in: path
      name: api_key
      description: ExchangeRate-API uses an API key embedded in the URL path (after /v6/).