Use a CLI npm ou REST com chave de API e créditos pré-pagos no seu backend. Envie Word, Excel, PDF ou imagem original; não converta antes. Chats Cursor, Claude, Codex e ChatGPT usam MCP em /agents. Agentes autônomos com Stripe Shared Payment Token ou carteira Tempo USDC usam MPP, HTTP 402; veja /agents e /blog/stripe-machine-payments-protocol.

Preciso de créditos antes de enviar?

Sim, para envios com chave de API. Crie a chave, compre créditos no painel ou com POST /api/v1/credits/checkout e envie. HTTP 402 em /api/v1/faxes significa saldo insuficiente, não um desafio MPP.

Posso usar chaves sf_test_?

Chaves de teste não enviam faxes reais. Use sf_live_. Guarde as chaves no servidor; nunca inclua em navegador ou aplicativo móvel.

O pacote oficial é a CLI npm @singlefax/cli. Exemplos Python, Go e PHP usam clientes HTTP padrão. Não há SDKs separados para Python, Go ou Ruby. Use /openapi.json com ferramentas OpenAPI para gerar um cliente.

É compatível com HIPAA?

Não. Não envie PHI por API pública, CLI, MCP ou MPP. Entidades sujeitas à HIPAA devem usar HIPAA Secure no site com BAA eletrônico.

REST · CLI · OpenAPI

Documentação API e CLI do SingleFax

Chave de API e créditos pré-pagos. CLI oficial npm ou exemplos REST em curl, Node, Python, Go e PHP. Aplicativos de chat devem usar MCP.

Criar chave de API CLI npm OpenAPI

CLI

npx @singlefax/cli send FILE --to +E164: envie Word, Excel, PDF ou imagem original, sem converter antes em PDF.

REST

POST /api/v1/faxes com Bearer sf_live_… e Idempotency-Key.

MCP para chat

Cursor, Claude, Codex, ChatGPT: OAuth, não chave de API. Instalar MCP.

Início rápido

Crie uma chave com permissões limitadas em Chaves de API: fax:send, fax:read, inbox:read, credits:read.
Compre créditos no painel ou por npx @singlefax/cli credits buy.
Envie pela CLI abaixo ou por POST /api/v1/faxes.

URL base https://api.singlefax.com, mesmos caminhos em https://singlefax.com. Chaves sf_test_ não enviam faxes reais. Não coloque chaves no navegador.

CLI

Node 20 ou superior. Configuração: SINGLEFAX_API_KEY ou ~/.config/singlefax/config.json. Envie Word, Excel, PowerPoint, PDF, texto ou imagem original; não converta antes. Não serve para MCP OAuth ou Stripe MPP.

terminal

export SINGLEFAX_API_KEY=sf_live_…

npx @singlefax/cli send ./document.docx --to +14155552671
npx @singlefax/cli send ./document.pdf --to +14155552671 --wait --json

quote, status, credits

npx @singlefax/cli quote --to +14155552671 --pages 12
npx @singlefax/cli status <id>
npx @singlefax/cli list
npx @singlefax/cli numbers
npx @singlefax/cli numbers buy
npx @singlefax/cli credits
npx @singlefax/cli credits buy --dollars 20

Enviar um fax

Uma solicitação: documento em base64 e destino. PDF, Word, Excel, PowerPoint, texto ou imagens. Idempotency-Key é obrigatório. Reusar uma chave com corpo diferente retorna 409.

terminal

PDF_B64="$(base64 < document.pdf | tr -d '\n')"

curl -sS https://api.singlefax.com/api/v1/faxes \
  -H "Authorization: Bearer $SINGLEFAX_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d "{\"to\":\"+14155552671\",\"base64\":\"$PDF_B64\"}"

send.mjs

import { readFile } from 'node:fs/promises'
import { randomUUID } from 'node:crypto'

const api = 'https://api.singlefax.com'
const key = process.env.SINGLEFAX_API_KEY
const pdf = await readFile('./document.pdf')

const res = await fetch(`${api}/api/v1/faxes`, {
  method: 'POST',
  headers: {
    Authorization: `Bearer ${key}`,
    'Content-Type': 'application/json',
    'Idempotency-Key': randomUUID(),
  },
  body: JSON.stringify({
    to: '+14155552671',
    base64: pdf.toString('base64'),
  }),
})
console.log(await res.json())

send.py

import base64, json, os, urllib.request, uuid
from pathlib import Path

API = "https://api.singlefax.com"
KEY = os.environ["SINGLEFAX_API_KEY"]
pdf = Path("document.pdf").read_bytes()

req = urllib.request.Request(
    f"{API}/api/v1/faxes",
    data=json.dumps({
        "to": "+14155552671",
        "base64": base64.b64encode(pdf).decode(),
    }).encode(),
    headers={
        "Authorization": f"Bearer {KEY}",
        "Content-Type": "application/json",
        "Idempotency-Key": str(uuid.uuid4()),
    },
    method="POST",
)
with urllib.request.urlopen(req) as res:
    print(res.read().decode())

send.go

package main

import (
	"bytes"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	pdf, err := os.ReadFile("document.pdf")
	if err != nil {
		panic(err)
	}
	body, _ := json.Marshal(map[string]string{
		"to":     "+14155552671",
		"base64": base64.StdEncoding.EncodeToString(pdf),
	})
	req, _ := http.NewRequest("POST", "https://api.singlefax.com/api/v1/faxes", bytes.NewReader(body))
	req.Header.Set("Authorization", "Bearer "+os.Getenv("SINGLEFAX_API_KEY"))
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Idempotency-Key", "send-document-1")
	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	out, _ := io.ReadAll(res.Body)
	fmt.Println(res.Status, string(out))
}

send.php

<?php
$pdf = base64_encode(file_get_contents('document.pdf'));
$ch = curl_init('https://api.singlefax.com/api/v1/faxes');
curl_setopt_array($ch, [
  CURLOPT_POST => true,
  CURLOPT_HTTPHEADER => [
    'Authorization: Bearer ' . getenv('SINGLEFAX_API_KEY'),
    'Content-Type: application/json',
    'Idempotency-Key: send-document-1',
  ],
  CURLOPT_POSTFIELDS => json_encode(['to' => '+14155552671', 'base64' => $pdf]),
  CURLOPT_RETURNTRANSFER => true,
]);
echo curl_exec($ch);

Arquivos maiores: envie o arquivo e depois o fax

A CLI cria um token de upload, envia os bytes por PUT e transmite com uploadToken. PUT também exige Bearer. É melhor do que incluir arquivo grande em JSON. Não converta antes em PDF.

terminal

UPLOAD=$(curl -sS https://api.singlefax.com/api/v1/uploads \
  -H "Authorization: Bearer $SINGLEFAX_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"contentType":"application/pdf"}')

UPLOAD_URL=$(printf '%s' "$UPLOAD" | python3 -c "import json,sys; print(json.load(sys.stdin)['uploadUrl'])")
TOKEN=$(printf '%s' "$UPLOAD" | python3 -c "import json,sys; print(json.load(sys.stdin)['uploadToken'])")

curl -sS -X PUT "$UPLOAD_URL" \
  -H "Authorization: Bearer $SINGLEFAX_API_KEY" \
  -H "Content-Type: application/pdf" \
  --data-binary @document.pdf

curl -sS https://api.singlefax.com/api/v1/faxes \
  -H "Authorization: Bearer $SINGLEFAX_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $(uuidgen)" \
  -d "{\"to\":\"+14155552671\",\"uploadToken\":\"$TOKEN\"}"

upload-send.mjs

import { readFile } from 'node:fs/promises'
import { randomUUID } from 'node:crypto'

const api = 'https://api.singlefax.com'
const key = process.env.SINGLEFAX_API_KEY
const auth = { Authorization: `Bearer ${key}` }
const pdf = await readFile('./document.pdf')

const upload = await fetch(`${api}/api/v1/uploads`, {
  method: 'POST',
  headers: { ...auth, 'Content-Type': 'application/json' },
  body: JSON.stringify({ contentType: 'application/pdf', maxBytes: pdf.byteLength }),
}).then((r) => r.json())

await fetch(upload.uploadUrl, {
  method: 'PUT',
  headers: { ...auth, 'Content-Type': 'application/pdf' },
  body: pdf,
})

const fax = await fetch(`${api}/api/v1/faxes`, {
  method: 'POST',
  headers: {
    ...auth,
    'Content-Type': 'application/json',
    'Idempotency-Key': randomUUID(),
  },
  body: JSON.stringify({ to: '+14155552671', uploadToken: upload.uploadToken }),
}).then((r) => r.json())

console.log(fax)

upload_send.py

import json, os, urllib.request, uuid
from pathlib import Path

API = "https://api.singlefax.com"
KEY = os.environ["SINGLEFAX_API_KEY"]
pdf = Path("document.pdf").read_bytes()

def request(url, *, data=None, method="GET", headers=None, content_type="application/json"):
    req = urllib.request.Request(
        url,
        data=data,
        headers={
            "Authorization": f"Bearer {KEY}",
            "Content-Type": content_type,
            **(headers or {}),
        },
        method=method,
    )
    with urllib.request.urlopen(req) as res:
        return res.read()

upload = json.loads(request(
    f"{API}/api/v1/uploads",
    method="POST",
    data=json.dumps({"contentType": "application/pdf", "maxBytes": len(pdf)}).encode(),
))
request(upload["uploadUrl"], method="PUT", data=pdf, content_type="application/pdf")
fax = request(
    f"{API}/api/v1/faxes",
    method="POST",
    data=json.dumps({"to": "+14155552671", "uploadToken": upload["uploadToken"]}).encode(),
    headers={"Idempotency-Key": str(uuid.uuid4())},
)
print(fax.decode())

upload_send.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	key := os.Getenv("SINGLEFAX_API_KEY")
	pdf, err := os.ReadFile("document.pdf")
	if err != nil {
		panic(err)
	}

	upBody, _ := json.Marshal(map[string]any{"contentType": "application/pdf", "maxBytes": len(pdf)})
	upReq, _ := http.NewRequest("POST", "https://api.singlefax.com/api/v1/uploads", bytes.NewReader(upBody))
	upReq.Header.Set("Authorization", "Bearer "+key)
	upReq.Header.Set("Content-Type", "application/json")
	upRes, err := http.DefaultClient.Do(upReq)
	if err != nil {
		panic(err)
	}
	defer upRes.Body.Close()
	var upload struct {
		UploadToken string `json:"uploadToken"`
		UploadUrl   string `json:"uploadUrl"`
	}
	json.NewDecoder(upRes.Body).Decode(&upload)

	put, _ := http.NewRequest("PUT", upload.UploadUrl, bytes.NewReader(pdf))
	put.Header.Set("Authorization", "Bearer "+key)
	put.Header.Set("Content-Type", "application/pdf")
	if _, err := http.DefaultClient.Do(put); err != nil {
		panic(err)
	}

	sendBody, _ := json.Marshal(map[string]string{"to": "+14155552671", "uploadToken": upload.UploadToken})
	faxReq, _ := http.NewRequest("POST", "https://api.singlefax.com/api/v1/faxes", bytes.NewReader(sendBody))
	faxReq.Header.Set("Authorization", "Bearer "+key)
	faxReq.Header.Set("Content-Type", "application/json")
	faxReq.Header.Set("Idempotency-Key", "send-document-1")
	faxRes, err := http.DefaultClient.Do(faxReq)
	if err != nil {
		panic(err)
	}
	defer faxRes.Body.Close()
	out, _ := io.ReadAll(faxRes.Body)
	fmt.Println(string(out))
}

upload-send.php

<?php
$key = getenv('SINGLEFAX_API_KEY');
$pdf = file_get_contents('document.pdf');

$ch = curl_init('https://api.singlefax.com/api/v1/uploads');
curl_setopt_array($ch, [
  CURLOPT_POST => true,
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer $key",
    'Content-Type: application/json',
  ],
  CURLOPT_POSTFIELDS => json_encode(['contentType' => 'application/pdf', 'maxBytes' => strlen($pdf)]),
  CURLOPT_RETURNTRANSFER => true,
]);
$upload = json_decode(curl_exec($ch), true);

$ch = curl_init($upload['uploadUrl']);
curl_setopt_array($ch, [
  CURLOPT_CUSTOMREQUEST => 'PUT',
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer $key",
    'Content-Type: application/pdf',
  ],
  CURLOPT_POSTFIELDS => $pdf,
  CURLOPT_RETURNTRANSFER => true,
]);
curl_exec($ch);

$ch = curl_init('https://api.singlefax.com/api/v1/faxes');
curl_setopt_array($ch, [
  CURLOPT_POST => true,
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer $key",
    'Content-Type: application/json',
    'Idempotency-Key: send-document-1',
  ],
  CURLOPT_POSTFIELDS => json_encode(['to' => '+14155552671', 'uploadToken' => $upload['uploadToken']]),
  CURLOPT_RETURNTRANSFER => true,
]);
echo curl_exec($ch);

Referência REST

Método	Caminho	Autenticação	Notas
POST	/api/v1/faxes	fax:send	Idempotency-Key required. JSON { to, base64 \| uploadToken } or multipart file.
GET	/api/v1/faxes	fax:read	List. Query limit, offset.
GET	/api/v1/faxes/{id}	fax:read	Status including latest delivery attempt.
POST	/api/v1/faxes/quote	fax:read	{ to, pages? \| base64? }, quote without charging.
POST	/api/v1/uploads	fax:send	Returns uploadToken + uploadUrl. PUT the bytes, then send with uploadToken.
GET	/api/v1/credits	credits:read	Prepaid balance.
POST	/api/v1/credits/checkout	credits:checkout	{ amountCents }. Stripe Checkout for a credit pack.
GET	/api/v1/received-faxes	inbox:read	Inbound inbox list. Query limit, cursor. No transcripts in list.
GET	/api/v1/received-faxes/{id}	inbox:read	Inbound detail with bounded transcript slice. HIPAA Secure content is omitted.
GET	/api/v1/numbers	fax:read	Active fax numbers.
POST	/api/v1/numbers	credits:checkout	{ sku?, country?, state? }, default inbound_30day. Returns checkoutUrl + reserved phoneNumber.
GET	/api/v1/skus	public	Catalog. Same shape as MCP list_skus.
POST	/api/v1/checkout	credits:checkout	{ sku }, credit_pack, inbound, subscriptions, lifetime.

Esquemas completos: openapi.json. Mudanças incompatíveis: política de versões, Sunset de 90 dias. HTTP 402 nesta API significa saldo insuficiente. MPP 402 só existe em POST /api/v1/machine/faxes.

Webhooks

Eventos assinados fax.queued, fax.delivered, fax.failed e credits.low_balance. Verifique SingleFax-Signature, t=,v1=, com o corpo original. HMAC-SHA256 de timestamp.payload. Adicione o endpoint em webhooks do painel.

verify.mjs

import { createHmac, timingSafeEqual } from 'node:crypto'

export function verifySingleFaxSignature(rawBody, signatureHeader, secret, toleranceSeconds = 300) {
  const parts = Object.fromEntries(signatureHeader.split(',').map((kv) => kv.split('=')))
  const timestamp = Number(parts.t)
  if (!Number.isFinite(timestamp) || !parts.v1) return false
  if (Math.abs(Math.floor(Date.now() / 1000) - timestamp) > toleranceSeconds) return false
  const expected = createHmac('sha256', secret).update(`${timestamp}.${rawBody}`).digest('hex')
  const a = Buffer.from(parts.v1)
  const b = Buffer.from(expected)
  return a.length === b.length && timingSafeEqual(a, b)
}

verify.py

import hashlib, hmac, time

def verify_singlefax_signature(payload: bytes, header: str, secret: str, tolerance: int = 300) -> bool:
    parts = dict(p.split("=", 1) for p in header.split(","))
    timestamp = int(parts["t"])
    if abs(int(time.time()) - timestamp) > tolerance:
        return False
    expected = hmac.new(
        secret.encode(),
        f"{timestamp}.".encode() + payload,
        hashlib.sha256,
    ).hexdigest()
    return hmac.compare_digest(expected, parts["v1"])

Restrições

Guarde chaves de API no servidor. Não inclua sf_live_ em uma página.
Não envie PHI. Entidades sujeitas à HIPAA usam HIPAA Secure no site com BAA eletrônico.
Destinos E.164 válidos. PDF, Word, Excel, PowerPoint, RTF, texto e imagens; veja MIME no OpenAPI. Não converta antes em PDF: fazemos isso antes do envio.
MCP de chat e Stripe MPP: /agents, mpp.md e MPP ou pagamento imediato.

Perguntas frequentes

Documentação legível por máquinas

Markdown simples e OpenAPI para rastreadores e agentes de programação. Os mesmos dados desta página.

Guia de autenticação Referência OpenAPI developers.md openapi.json auth.md llms.txt MCP e agentes MPP ou pagamento imediato versioning.md