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For builders & power users

The fax line your AI agent can use

Many government agencies, and some offices and courts, still take fax. Your AI assistant cannot dial a fax machine by itself — but it can use fax.monster when you give it a key and money to spend.

You
AI assistant
fax.monster
Fax machine

A key you control

You create an API key in your account — like a house key you can take back anytime. Only a signed-in human can make keys. Agents never sign up on their own.

Prepaid balance

You add credits like a gift card ($5.00 and up). Each fax send or number rental spends from that balance when you are not on Business or a private rental allowance.

How to set it up

Three steps for the human. Then your AI does the rest.

  1. 1

    Sign in and add credit

    Use Google or an email link. Add prepaid credits from your account page.

  2. 2

    Create a key

    On the Developers page, make an API key. Copy it somewhere safe.

  3. 3

    Paste into your AI app

    Add the MCP plug below to Claude Desktop, Cursor, or any tool that supports MCP. MCP is a plug that lets AI assistants like Claude use fax.monster.

Example you can try

Ask Claude: “Fax this signed lease to +1 555 555 1234 and tell me when it's delivered.”

What your agent can do

  • Send a fax from a PDF you uploaded
  • Check if a fax finished or failed
  • Rent its own private fax number for 30 days
  • List and download faxes that arrived
  • Point webhooks at your server for events

Safety

  • You see every fax your agents send in your dashboard.
  • Daily send limits help stop runaway bots.
  • Revoke a key instantly if it leaks.
  • Failed faxes do not use your page allowance or prepaid API credits. Fax only ($1.99): one free retry, then email us for a refund if it still fails.

Price

$1.99 per fax from the shared number (up to 50 pages). $4.99 to rent a private number for 30 days. Or subscribe to Business for an office line with a bigger monthly bucket. With an active Fax Monster Business subscription, API and MCP sends use your Business monthly page bucket (1,000 pages in + out combined). They do not spend prepaid API credits unless you send from the shared number without Business or rent a separate API private number.

MCP config (copy and paste)

Cursor and other apps that take a URL

{
  "mcpServers": {
    "fax-monster": {
      "url": "https://fax.monster/mcp",
      "headers": { "Authorization": "Bearer fm_live_…" }
    }
  }
}

Claude Desktop (uses the free mcp-remote helper, needs Node.js)

{
  "mcpServers": {
    "fax-monster": {
      "command": "npx",
      "args": [
        "mcp-remote", "https://fax.monster/mcp",
        "--header", "Authorization: Bearer fm_live_…"
      ]
    }
  }
}

Replace fm_live_… with your real key. Technical docs & API keys · MCP server setup · OpenAPI

Questions

Can my AI create its own account?
No. A human must sign in and create keys. That keeps billing and abuse tied to a real person.
What is MCP?
MCP is a plug that lets AI assistants like Claude call tools on fax.monster — send fax, check status, and more.
Is there a command-line tool?
A CLI package is coming soon. Today use the API or MCP.
US only?
Yes. Destinations must be US fax numbers we can reach.