openapi: 3.1.0
info:
  title: Western Union Mass Payments Balances API
  description: The Western Union Mass Payments API enables financial institutions and enterprise customers to send up to 10,000 international payments in a single batch across 130+ currencies in 200+ countries and territories. The API supports payment lifecycle management including batch creation, adding payments, FX quotes, committing, and tracking. Authentication requires mutual TLS (mTLS) client certificates provided by Western Union upon partnership enrollment.
  version: v1
  contact:
    name: Western Union Partnership Program
    url: https://developer.westernunion.com/getting-started.html
    email: wuconnect@westernunion.com
  license:
    name: Western Union Partner Terms
    url: https://developer.westernunion.com/getting-started.html
servers:
- url: https://api.westernunion.com
  description: Production endpoint
- url: https://api-sandbox.westernunion.com
  description: Sandbox for testing
tags:
- name: Balances
  description: Holding balance inquiry.
paths:
  /HoldingBalance/{clientId}/{currencyCode}:
    get:
      operationId: getHoldingBalance
      summary: Get Holding Balance
      description: Returns the current holding balance for the specified currency in the partner's WU account. Used to verify sufficient funds before initiating payments.
      tags:
      - Balances
      security:
      - mtlsAuth: []
      parameters:
      - name: clientId
        in: path
        required: true
        schema:
          type: string
        description: The partner's Western Union client ID.
      - name: currencyCode
        in: path
        required: true
        schema:
          type: string
          pattern: ^[A-Z]{3}$
        description: ISO 4217 currency code (e.g., USD, EUR, GBP).
      responses:
        '200':
          description: Holding balance for the specified currency.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/HoldingBalanceResponse'
        '401':
          description: Authentication failed.
        '404':
          description: Client or currency not found.
components:
  schemas:
    HoldingBalance:
      type: object
      properties:
        currencyCode:
          type: string
          description: ISO 4217 currency code.
        amount:
          type: number
          format: double
          description: Available balance amount.
    HoldingBalanceResponse:
      type: object
      properties:
        clientId:
          type: string
        currencyCode:
          type: string
        balance:
          $ref: '#/components/schemas/HoldingBalance'
  securitySchemes:
    mtlsAuth:
      type: mutualTLS
      description: Mutual TLS authentication using client certificates provided by Western Union upon enrollment in the Partnership Program. Include the certificate and key with every request.