SendFaxFast

Calculate the pay-per-fax price for sending a fax to a specific number. No API key required. Supported: USA, Canada, Australia, New Zealand and 39 more countries (same list as sendfaxfast.com); premium-rate numbers are not supported.

{
  "type": "object",
  "properties": {
    "fax_number": {
      "type": "string",
      "description": "Recipient fax number in E.164 format (e.g. +12125550100 for USA, +61212345678 for Australia, +911123456789 for India)"
    },
    "pages": {
      "type": "integer",
      "description": "Number of pages in the document (default: 1)",
      "default": 1,
      "minimum": 1,
      "maximum": 100
    }
  },
  "required": [
    "fax_number"
  ]
}

Send a PDF document to a fax number. WITHOUT API key: returns a Stripe checkout link (pay-per-fax from $2.49) – the fax is sent after the user pays. WITH a Mini/Flex subscription key (sff_...): sends immediately from the subscription quota. The document must be a direct, publicly accessible HTTPS link to a PDF (max. 10 MB). Supported: USA, Canada, Australia, New Zealand and 39 more countries (same list as sendfaxfast.com); premium-rate numbers are not supported. Each call transmits (or, for pay-per-fax, prepares the checkout for) a real fax to the given number. DOCUMENT (exactly one): "upload_id" from create_upload_link (for files on the user's device), "file" (a file attached in ChatGPT, filled in automatically), "document_url" (direct public HTTPS link to a PDF) or "document_base64" (tiny files only, max. 700 KB). For an attachment that is not available as "file", create_upload_link provides an upload link. The result states whether the fax was sent, scheduled or is awaiting payment.

{
  "type": "object",
  "properties": {
    "fax_number": {
      "type": "string",
      "description": "Recipient fax number in E.164 format (e.g. +12125550100)"
    },
    "document_url": {
      "type": "string",
      "description": "Direct, publicly accessible HTTPS URL of the PDF document to fax (no login or preview pages) Alternative to upload_id / file."
    },
    "email": {
      "type": "string",
      "description": "Customer email for payment receipt and delivery confirmation (optional for pay-per-fax)"
    },
    "scheduled_at": {
      "type": "string",
      "description": "ISO 8601 datetime to schedule the fax (e.g. 2026-10-08T09:00:00-05:00). Leave empty to send immediately."
    },
    "upload_id": {
      "type": "string",
      "description": "upload_id returned by create_upload_link (after the user uploaded the file). One-time use."
    },
    "file": {
      "type": "object",
      "description": "ChatGPT: the fax document the user attached in the chat (PDF, JPG or PNG). Filled in automatically by ChatGPT.",
      "properties": {
        "download_url": {
          "type": "string"
        },
        "file_id": {
          "type": "string"
        },
        "mime_type": {
          "type": "string"
        },
        "file_name": {
          "type": "string"
        }
      },
      "required": [
        "download_url",
        "file_id"
      ],
      "additionalProperties": false
    },
    "document_base64": {
      "type": "string",
      "description": "Only for very small files (max. 700 KB): the PDF, JPG or PNG as base64 or data: URI. Prefer create_upload_link."
    },
    "document_name": {
      "type": "string",
      "description": "Optional: original file name of the document (e.g. \"invoice.pdf\"), shown on the transmission report. Not needed with upload_id or file."
    }
  },
  "required": [
    "fax_number"
  ]
}

Check the delivery status of a fax. Use token for pay-per-fax orders, fax_id for subscription orders (fax_id requires your API key; only your own faxes are visible).

{
  "type": "object",
  "properties": {
    "token": {
      "type": "string",
      "description": "Token returned by send_fax for pay-per-fax orders"
    },
    "fax_id": {
      "type": "integer",
      "description": "Fax ID returned by send_fax for subscription orders (requires API key)"
    }
  }
}

Get subscription plan details, remaining fax quota, and billing period. Requires your subscription API key (sff_...).

{
  "type": "object",
  "properties": {},
  "additionalProperties": false
}

List recent faxes sent from this subscription account. Requires your subscription API key (sff_...).

{
  "type": "object",
  "properties": {
    "limit": {
      "type": "integer",
      "description": "Number of results to return (1–50, default: 10)",
      "default": 10,
      "minimum": 1,
      "maximum": 50
    },
    "offset": {
      "type": "integer",
      "description": "Pagination offset (default: 0)",
      "default": 0,
      "minimum": 0
    }
  }
}

Creates a secure one-time upload link (valid 30 minutes) for the fax document (PDF, JPG or PNG, max. 10 MB) – upload from phone or computer by drag & drop, file picker or camera. For files on the user's device, or chat attachments that are not available as send_fax's "file" parameter. The user opens upload_url and uploads the file; send_fax then accepts the returned upload_id. Creating a link sends nothing and costs nothing.

{
  "type": "object",
  "properties": {},
  "additionalProperties": false
}