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Fax MCP server

Give your AI agent a real fax line. It can send faxes, check delivery, rent its own US number, read faxes that come back, and ping your server with webhooks. One API key does it all.

Server URL
https://fax.monster/mcp
Registry name
monster.fax/fax-monster

Tools your agent gets

  • send_fax

    Send a PDF to a US fax number.

  • get_fax_status

    Check if a fax was delivered.

  • list_sent_faxes

    List recent faxes your agent sent.

  • rent_private_number

    Rent your own US fax number for 30 days.

  • list_private_numbers

    See the numbers you rent.

  • renew_private_number

    Keep a number for another 30 days.

  • release_private_number

    Give a number back early.

  • list_inbound_faxes

    See faxes that came in.

  • download_inbound_fax

    Get a short-lived link to an incoming PDF.

  • set_webhook

    Tell us where to ping your server when something happens.

  • account_balance

    Check prepaid credit and prices.

  • create_top_up_link

    Make a payment link so a human can add credit.

Connect your client

Replace fm_live_YOUR_KEY with a key from the Developers page.

Cursor (and other clients with remote URL support)

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

Claude Code

claude mcp add --transport http fax-monster https://fax.monster/mcp \
  --header "Authorization: Bearer fm_live_YOUR_KEY"

Claude Desktop (via mcp-remote)

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

How keys work

A signed-in human with a verified email creates keys (fm_live_…) and can revoke them anytime. Send the key as Authorization: Bearer. Limits: 15 sends a day and 120 requests a minute per key on prepaid credits.

Webhooks

Set one URL and get fax.outbound.delivered, fax.outbound.failed and fax.inbound.received events, signed with an HMAC secret so you know they came from us.

Billing

Prepaid credits: $1.99 per fax from the shared number, $4.99 per 30-day private number. Top up from $5.00. 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.

Questions developers ask

Which MCP clients work?
Any client that supports remote MCP servers over Streamable HTTP with a custom Authorization header, such as Cursor and Claude Code. Claude Desktop can connect through the mcp-remote bridge shown on this page.
Can my agent receive faxes?
Yes. Rent a private number (or use your Business number), then your agent can list incoming faxes and download the PDFs. A webhook can tell your server the moment one arrives.
How is agent usage billed on Business?
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.
What happens if a fax fails?
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.
Can an agent sign up by itself?
No. A human signs in, verifies their email, and creates the API key. You can revoke a key at any time.

API keys & docsOpenAPIserver.jsonPlain-language overview