Phaxio Fax API
★ Only Publicly Available OpenAPI DocumentCommunicationsVoice Telephonybasic13 EndpointsREST
For Agents
Send and receive faxes programmatically, provision phone numbers, retrieve fax content, and look up available area codes for fax number assignment.
Use for: I need to send a fax to a phone number with a PDF attachment, I want to provision a new fax phone number in a specific area code, Check whether a fax was successfully delivered, List all faxes sent in the last 24 hours
Not supported: Does not handle email, SMS, voice calls, or document signing — use for fax transmission and phone number provisioning only.
Jentic publishes the only available OpenAPI specification for Phaxio Fax API, keeping it validated and agent-ready. Phaxio provides a programmatic interface for sending and receiving faxes, provisioning phone numbers, and managing fax content. The API supports batch fax delivery, fax status tracking, phone number management across US and Canadian area codes, and account-level reporting with 13 endpoints covering the full fax lifecycle.
Install Jentic One Beta
Connect the Phaxio Fax API to your agent
Jentic One is a self-hosted execution layer for AI agents. It lets your agent call the Phaxio Fax API, or any other public or private API you need. You set the rules, the agent never sees your credentials, and every call is logged.
Two steps, two machines. Install the instance in a safe environment, then register your agent from wherever it runs.
1
Step 1: Jentic One Host machine
# On the machine that will host your Jentic One instance:
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh2
Step 2: Agent machine
# On the machine where your agent runs (keep this separate from the instance):
curl -fsSL https://raw.githubusercontent.com/jentic/jentic-one/main/tools/install.sh | sh
jentic register # connects your agent to your Jentic One instanceJentic One is in public beta. The setup above keeps your agent separate from the instance, which is what you want before using real credentials: an agent running as the same OS user as Jentic One can read its stored keys directly. Just evaluating? A single local install is fine to start. See the secure deployment guide for the tiers.
Capabilities
What an agent can do with Phaxio Fax API.
Send faxes to one or multiple recipients with file attachments or content URLs
Receive inbound faxes on provisioned phone numbers with webhook notifications
Provision and release dedicated fax phone numbers across US and Canadian area codes
Retrieve sent and received fax content as PDF files
Track fax delivery status including page count, duration, and error details
Look up available area codes for fax number provisioning by state or region
Monitor account usage including pages sent, pages received, and current balance
Use Cases
Patterns agents use Phaxio Fax API for, with concrete tasks.
★ Automated Document Faxing
Send documents via fax to recipients who require fax-based delivery, such as healthcare providers, legal offices, and government agencies. Phaxio handles the phone line connection, retry logic, and delivery confirmation automatically. Supports batch sending to multiple recipients in a single API call with individual delivery tracking per recipient.
Send a fax to +1-555-0100 with a PDF file attachment and confirm delivery status within 5 minutes
Inbound Fax Reception
Receive faxes on dedicated phone numbers and process them programmatically. Phaxio provisions local or toll-free numbers, receives incoming faxes, and delivers the content as downloadable files via webhook notification. Useful for digitizing fax workflows in healthcare, legal, and insurance industries where counterparties still rely on fax communication.
Provision a new fax number in area code 212 and configure a webhook URL to receive inbound fax notifications
Fax Number Management
Provision, manage, and release dedicated fax phone numbers across US and Canadian area codes. Look up available area codes by region, assign numbers for specific departments or use cases, and release numbers when no longer needed. Each number supports both sending and receiving faxes.
List all available area codes in New York state and provision a fax number from the 718 area code
AI Agent Fax Integration via Jentic
AI agents can send and track faxes through Jentic without managing Phaxio credentials directly. An agent searches for fax-sending operations, loads the endpoint schema, and executes the call with Jentic handling authentication. This enables agents to fulfill requests like sending legal documents or healthcare forms via fax as part of a larger automated workflow.
Search Jentic for 'send a fax with PDF attachment', load the Phaxio send fax operation schema, and execute the call to fax a document to +1-555-0199
Key Endpoints
13 endpoints — jentic publishes the only available openapi specification for phaxio fax api, keeping it validated and agent-ready.
METHOD
PATH
DESCRIPTION
POST
/faxes
Send a fax to one or more recipients
GET
/faxes
List faxes with filters for date range and status
GET
/faxes/{id}
Get detailed status of a specific fax
GET
/faxes/{id}/file
Download fax content as PDF
POST
/faxes/{id}/cancel
Cancel a queued fax
POST
/faxes/{id}/resend
Resend a previously sent fax
GET
/phone_numbers
List provisioned fax phone numbers
GET
/public/area_codes
Look up available area codes for provisioning
POST
/faxes
Send a fax to one or more recipients
GET
/faxes
List faxes with filters for date range and status
GET
/faxes/{id}
Get detailed status of a specific fax
GET
/faxes/{id}/file
Download fax content as PDF
POST
/faxes/{id}/cancel
Cancel a queued fax
POST
/faxes/{id}/resend
Resend a previously sent fax
GET
/phone_numbers
List provisioned fax phone numbers
GET
/public/area_codes
Look up available area codes for provisioning
Why Jentic?
Three things that make agents converge on Jentic-routed access.
Credential isolation
Phaxio API key and secret are stored encrypted in the Jentic MAXsystem vault. Agents receive scoped Basic auth headers at execution time — raw credentials never enter the agent context.
Intent-based discovery
Agents search by intent (e.g., 'send a fax with PDF') and Jentic returns matching Phaxio operations with input schemas including required parameters like recipient number and file content.
Time to first call
Direct Phaxio integration: 1-2 days for auth setup, webhook configuration, and error handling. Through Jentic: under 1 hour — search, load schema, execute.
Related APIs
Alternatives and complements available in the Jentic catalogue.
FAQs
Specific to using Phaxio Fax API through Jentic.
Why is there no official OpenAPI spec for Phaxio Fax API?
Phaxio does not publish an OpenAPI specification. Jentic generates and maintains this spec so that AI agents and developers can call Phaxio Fax API via structured tooling. It is validated against the live API and kept up to date. Get started at https://app.jentic.com/sign-up.
What authentication does the Phaxio Fax API use?
Phaxio uses HTTP Basic authentication. Your API key serves as the username and your API secret serves as the password. Through Jentic, these credentials are stored encrypted in the MAXsystem vault, so agents never handle raw secrets directly.
Can I send a fax to multiple recipients with the Phaxio API?
Yes. The POST /faxes endpoint accepts multiple recipient phone numbers in a single request. Each recipient gets an individual delivery status that you can track via GET /faxes/{id}. Supported file formats include PDF, DOC, DOCX, and plain text.
What are the rate limits for the Phaxio Fax API?
Phaxio rate limits are tied to your account plan. The API returns HTTP 429 when limits are exceeded. Fax delivery itself is constrained by phone line capacity rather than API rate limits, so large batch sends are queued and processed sequentially per recipient number.
How do I retrieve a received fax as a PDF through Jentic?
Search Jentic for 'download fax content' to find the GET /faxes/{id}/file operation. Load the schema, provide the fax ID from your inbound webhook payload, and execute the call. Jentic returns the PDF binary content with the correct content-type header.
Which area codes can I provision fax numbers in?
Use GET /public/area_codes to retrieve the full list of available area codes. You can filter by state or country. Phaxio supports US and Canadian area codes including local and toll-free numbers. Provisioning is immediate once you select an available number.
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