curl --request GET \
  --url https://api-sandbox.endl.io/api/v0/accounts/cus_9FpQ2LmZ8sW4TxKn1BvD/acct_7Kq2XbN4mR8vLp1DcYtZ/balance \
  --header 'API-KEY: <api-key>' \
  --header 'Api-Version: 2026-09.1'

{
  "accountId": "acct_8f2a1c4e9b7d43a6",
  "available": { "amount": "12450.00", "currency": "USD" },
  "asOf": "2026-09-30T06:14:02Z"
}

{
  "code": 400,
  "message": "User id is required",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRACC_1000",
      "message": "User id is required",
      "field": "userId"
    }
  ]
}

{
  "code": 401,
  "message": "Partner API key required",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRCORE_1004",
      "message": "Partner API key required",
      "field": null
    }
  ]
}

{
  "code": 403,
  "message": "Insufficient permissions",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRCORE_1005",
      "message": "Insufficient permissions",
      "field": null
    }
  ]
}

{
  "code": 404,
  "message": "User with ID 'cus_…' not found",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRREF_1001",
      "message": "User with ID 'cus_…' not found",
      "field": "userId"
    }
  ]
}

{
  "code": 405,
  "message": "HTTP … is not supported for this endpoint",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRCORE_1001",
      "message": "HTTP … is not supported for this endpoint",
      "field": null
    }
  ]
}

{
  "code": 409,
  "message": "Balance is not available for this account's provider",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRACC_1003",
      "message": "Balance is not available for this account's provider",
      "field": null
    }
  ]
}

{
  "code": 429,
  "message": "Rate limit exceeded, please retry later",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRCORE_1006",
      "message": "Rate limit exceeded, please retry later",
      "field": null
    }
  ]
}

{
  "code": 500,
  "message": "An error occurred while processing your request",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRCORE_1000",
      "message": "An error occurred while processing your request",
      "field": null
    }
  ]
}

{
  "code": 502,
  "message": "The balance could not be retrieved. Please try again in a moment",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRACC_1011",
      "message": "The balance could not be retrieved. Please try again in a moment",
      "field": null
    }
  ]
}

{
  "code": 503,
  "message": "The account provider is temporarily unavailable. Please try again later",
  "status": "ERROR",
  "data": null,
  "errors": [
    {
      "code": "ERRACC_1012",
      "message": "The account provider is temporarily unavailable. Please try again later",
      "field": null
    }
  ]
}