Fax API

List and track fax (MMS/T.38) transmissions on Telnyx-backed fax numbers (sending flows through the Messaging API) Base path: /api/v1/fax Endpoint count: 3

title: “Errors worth branching on” description: “Per-endpoint failure templates matching the envelope — what actually fires, what to retry, what to surface to the operator.”

Errors worth branching on

These five failures cover the fax send (POST /api/v1/fax), on every send from the document viewer. Each block below is a full { error, meta } envelope as the API returns it, and the matrix at the bottom answers retry vs surface for the same five classes. For the platform-wide decision table these branches plug into, see the error handling guide.

401 — Unauthorized

  {
    "error": {
      "code": "UNAUTHORIZED",
      "message": "The API key is invalid, expired, or lacks the required scope.",
      "status": 401
    },
    "meta": {
      "request_id": "req_faxa1",
      "timestamp": "2026-09-03T12:00:00Z"
    }
  }

A 401 on this page is the bearer key failing before the route ran — it never means the resource is wrong. Rotate the key or re-mint the scoped token; retrying the same request changes nothing.

403 — Forbidden

  {
    "error": {
      "code": "FORBIDDEN",
      "message": "The key is valid but does not have the scope this operation requires.",
      "status": 403
    },
    "meta": {
      "request_id": "req_faxa1f",
      "timestamp": "2026-09-03T12:00:00Z"
    }
  }

A 403 means the key authenticated but the operation is gated by scope — check the key’s scopes on the developer page; a 403 is never a data-not-found shape.

422 — Schema

  {
    "error": {
      "code": "VALIDATION_ERROR",
      "message": "The request failed input validation.",
      "status": 422,
      "details": { "field": "media_url", "value": "ftp://file", "expected": "an https:// URL to a PDF or TIFF" }
    },
    "meta": {
      "request_id": "req_faxb2",
      "timestamp": "2026-09-03T12:00:00Z"
    }
  }

A 422 means the payload did not match the request schema — branch on error.details.field and resend with an https:// media_url to a PDF or TIFF instead of blind-retrying the same body.

429 — Rate

  {
    "error": {
      "code": "RATE_LIMITED",
      "message": "Too many requests in the current window.",
      "status": 429,
      "details": { "retry_after": 12 }
    },
    "meta": {
      "request_id": "req_faxc3",
      "timestamp": "2026-09-03T12:00:00Z",
      "docs_url": "https://docs.orbit.devotel.io/errors/RATE_LIMITED"
    }
  }

The Retry-After header and error.details.retry_after are both set on every 429 — resend the SAME request after the lower of the two.

402 — Feature gate

  {
    "error": {
      "code": "FAX_SENDER_NOT_PROVISIONED",
      "message": "No fax-capable sender is provisioned for this tenant.",
      "status": 402,
      "details": { "required_capability": "fax_outbound" }
    },
    "meta": {
      "request_id": "req_faxd4",
      "timestamp": "2026-09-03T12:00:00Z"
    }
  }

Surface provisioning — the retry succeeds only once the number is fax-capable.

60-second retry matrix

Class	Meaning	Branch response
401 `UNAUTHORIZED`	the bearer key itself fails	Surface. Rotate the key or re-mint the scoped token; do not retry the same request.
403 `FORBIDDEN`	the key lacks this operation’s scope	Surface. Fix the key’s scope set; a retry with the same key never heals it.
422 `VALIDATION_ERROR`	the payload does not match the schema	Fix, then resend intentionally. Branch on `error.details.field`; a blind retry repeats the same 422.
429 `RATE_LIMITED`	the window quota is exhausted	Retry after `error.details.retry_after` (or the `Retry-After` header) with the same request body.
`FAX_SENDER_NOT_PROVISIONED` (402 feature gate)	Surface provisioning	Branch on `error.code`. The retry succeeds only once the number is fax-capable.

List fax message history

GET /api/v1/fax

Cursor-paginated history of fax (MMS/T.38) transmissions for the authenticated tenant. Returns the standard paginated envelope; pass cursor from a prior page’s meta.pagination.cursor to page forward.

string

Opaque pagination cursor from a prior page’s meta.pagination.cursor. Omit for the first page.

integer

Page size (1–200, default 25).

string (enum: true|false)

Sandbox opt-in for Clerk-session-authenticated requests. Set to true to route the call through the test-mode pipeline: no real provider delivery, no credits deducted, response meta.test_mode: true. Ignored for live API keys (dv_live_sk_*) — server-to-server clients must use a test-prefixed key (dv_test_sk_*) to exercise sandbox. Test-prefixed keys unconditionally enable sandbox regardless of this header.

cURL

curl -X GET "https://api.orbit.devotel.io/api/v1/fax" \
  -H "X-API-Key: dv_live_sk_your_key_here" 

Node.js

import { Orbit } from '@devotel-orbit/node'

const orbit = new Orbit({
  apiKey: process.env.ORBIT_API_KEY!,
})

const res = await fetch('https://api.orbit.devotel.io/api/v1/fax', {
  method: 'GET',
  headers: {
    'X-API-Key': process.env.ORBIT_API_KEY!,
  },
})
console.log(await res.json())

Python

import os, requests

headers = {"X-API-Key": os.environ["ORBIT_API_KEY"]}
r = requests.get("https://api.orbit.devotel.io/api/v1/fax", headers=headers)
print(r.json())

package main

import (
	"bytes"
	"net/http"
	"os"
)

func main() {
	req, _ := http.NewRequest("GET", "https://api.orbit.devotel.io/api/v1/fax", nil)
	req.Header.Set("X-API-Key", os.Getenv("ORBIT_API_KEY"))

	http.DefaultClient.Do(req)
}

Ruby

require 'net/http'
require 'json'

uri = URI('https://api.orbit.devotel.io/api/v1/fax')
req = Net::HTTP::Get.new(uri)
req['X-API-Key'] = ENV['ORBIT_API_KEY']


res = Net::HTTP.start(uri.host, uri.port, use_ssl: true) { |h| h.request(req) }
puts res.body

PHP

<?php
$ch = curl_init('https://api.orbit.devotel.io/api/v1/fax');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');
curl_setopt($ch, CURLOPT_HTTPHEADER, [
  'X-API-Key: ' . getenv('ORBIT_API_KEY'),

]);

echo curl_exec($ch);

{
  "data": [
    {
      "id": "msg_3f6a81c2d4e5471a9b0c2d5e",
      "channel": "sms",
      "status": "delivered",
      "external_id": null,
      "created_at": "1970-01-01T00:00:00.000Z"
    }
  ],
  "meta": {
    "request_id": "req_sample",
    "timestamp": "1970-01-01T00:00:00.000Z",
    "pagination": {
      "cursor": null,
      "has_more": false,
      "total": 0
    }
  }
}

Get fax message details

GET /api/v1/fax/{id}

Fetch a single fax (MMS/T.38) message by its ID, scoped to the authenticated tenant. Returns 404 when no fax message with the given ID exists for the tenant.

string

required

Fax message ID (msg_…).

string (enum: true|false)

cURL

curl -X GET "https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3" \
  -H "X-API-Key: dv_live_sk_your_key_here" 

Node.js

import { Orbit } from '@devotel-orbit/node'

const orbit = new Orbit({
  apiKey: process.env.ORBIT_API_KEY!,
})

const res = await fetch('https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3', {
  method: 'GET',
  headers: {
    'X-API-Key': process.env.ORBIT_API_KEY!,
  },
})
console.log(await res.json())

Python

import os, requests

headers = {"X-API-Key": os.environ["ORBIT_API_KEY"]}
r = requests.get("https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3", headers=headers)
print(r.json())

package main

import (
	"bytes"
	"net/http"
	"os"
)

func main() {
	req, _ := http.NewRequest("GET", "https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3", nil)
	req.Header.Set("X-API-Key", os.Getenv("ORBIT_API_KEY"))

	http.DefaultClient.Do(req)
}

Ruby

require 'net/http'
require 'json'

uri = URI('https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3')
req = Net::HTTP::Get.new(uri)
req['X-API-Key'] = ENV['ORBIT_API_KEY']


res = Net::HTTP.start(uri.host, uri.port, use_ssl: true) { |h| h.request(req) }
puts res.body

PHP

<?php
$ch = curl_init('https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');
curl_setopt($ch, CURLOPT_HTTPHEADER, [
  'X-API-Key: ' . getenv('ORBIT_API_KEY'),

]);

echo curl_exec($ch);

{
  "data": {
    "id": "msg_3f6a81c2d4e5471a9b0c2d5e",
    "channel": "sms",
    "status": "delivered",
    "external_id": null,
    "created_at": "1970-01-01T00:00:00.000Z"
  },
  "meta": {
    "request_id": "req_sample",
    "timestamp": "1970-01-01T00:00:00.000Z"
  }
}

Get fax delivery status

GET /api/v1/fax/{id}/status

Retrieve the current delivery status of a fax (MMS/T.38) transmission by its message ID. Resolves the provider-side external_id first, then returns the live provider status (cached for ~10s per tenant). Returns 404 when no fax message exists for the tenant OR the transmission has not yet been dispatched (no external_id).

string

required

Fax message ID (msg_…).

string (enum: true|false)

cURL

curl -X GET "https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3/status" \
  -H "X-API-Key: dv_live_sk_your_key_here" 

Node.js

import { Orbit } from '@devotel-orbit/node'

const orbit = new Orbit({
  apiKey: process.env.ORBIT_API_KEY!,
})

const res = await fetch('https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3/status', {
  method: 'GET',
  headers: {
    'X-API-Key': process.env.ORBIT_API_KEY!,
  },
})
console.log(await res.json())

Python

import os, requests

headers = {"X-API-Key": os.environ["ORBIT_API_KEY"]}
r = requests.get("https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3/status", headers=headers)
print(r.json())

package main

import (
	"bytes"
	"net/http"
	"os"
)

func main() {
	req, _ := http.NewRequest("GET", "https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3/status", nil)
	req.Header.Set("X-API-Key", os.Getenv("ORBIT_API_KEY"))

	http.DefaultClient.Do(req)
}

Ruby

require 'net/http'
require 'json'

uri = URI('https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3/status')
req = Net::HTTP::Get.new(uri)
req['X-API-Key'] = ENV['ORBIT_API_KEY']


res = Net::HTTP.start(uri.host, uri.port, use_ssl: true) { |h| h.request(req) }
puts res.body

PHP

<?php
$ch = curl_init('https://api.orbit.devotel.io/api/v1/fax/num_8fb2d1b7c00c4ec9a1d3f5e7b9c1d3/status');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'GET');
curl_setopt($ch, CURLOPT_HTTPHEADER, [
  'X-API-Key: ' . getenv('ORBIT_API_KEY'),

]);

echo curl_exec($ch);

{
  "data": {
    "id": "msg_3f6a81c2d4e5471a9b0c2d5e",
    "status": "delivered"
  },
  "meta": {
    "request_id": "req_sample",
    "timestamp": "1970-01-01T00:00:00.000Z"
  }
}

API Reference

All Endpoints

Fax API

Fax API

title: “Errors worth branching on” description: “Per-endpoint failure templates matching the envelope — what actually fires, what to retry, what to surface to the operator.”

Errors worth branching on

401 — Unauthorized

403 — Forbidden

422 — Schema

429 — Rate

402 — Feature gate

60-second retry matrix

List fax message history

Get fax message details

Get fax delivery status

​Fax API

​title: “Errors worth branching on” description: “Per-endpoint failure templates matching the envelope — what actually fires, what to retry, what to surface to the operator.”

​Errors worth branching on

​401 — Unauthorized

​403 — Forbidden

​422 — Schema

​429 — Rate

​402 — Feature gate

​60-second retry matrix

​List fax message history

​Get fax message details

​Get fax delivery status

Fax API

title: “Errors worth branching on” description: “Per-endpoint failure templates matching the envelope — what actually fires, what to retry, what to surface to the operator.”

Errors worth branching on

401 — Unauthorized

403 — Forbidden

422 — Schema

429 — Rate

402 — Feature gate

60-second retry matrix

List fax message history

Get fax message details

Get fax delivery status